def inverse_laplace_transform(expr, s, t, **assumptions): """Calculate inverse Laplace transform of X(s) and return x(t). The unilateral Laplace transform cannot determine x(t) for t < 0 unless given additional information in the way of assumptions. The assumptions are: dc -- x(t) = constant so X(s) must have the form constant / s causal -- x(t) = 0 for t < 0. ac -- x(t) = A cos(a * t) + B * sin(b * t) """ if expr.is_Equality: return sym.Eq( inverse_laplace_transform(expr.args[0], s, t, **assumptions), inverse_laplace_transform(expr.args[1], s, t, **assumptions)) if expr.has(t): raise ValueError( 'Cannot inverse Laplace transform for expression %s that depends on %s' % (expr, t)) const, cresult, uresult = inverse_laplace_transform1( expr, s, t, **assumptions) return inverse_laplace_make(t, const, cresult, uresult, **assumptions)
def test_as_integral(): from sympy import Function, Integral f = Function("f") assert mellin_transform(f(x), x, s).rewrite("Integral") == Integral( x ** (s - 1) * f(x), (x, 0, oo) ) assert fourier_transform(f(x), x, s).rewrite("Integral") == Integral( f(x) * exp(-2 * I * pi * s * x), (x, -oo, oo) ) assert laplace_transform(f(x), x, s).rewrite("Integral") == Integral( f(x) * exp(-s * x), (x, 0, oo) ) assert ( str( 2 * pi * I * inverse_mellin_transform(f(s), s, x, (a, b)).rewrite("Integral") ) == "Integral(x**(-s)*f(s), (s, _c - oo*I, _c + oo*I))" ) assert ( str(2 * pi * I * inverse_laplace_transform(f(s), s, x).rewrite("Integral")) == "Integral(f(s)*exp(s*x), (s, _c - oo*I, _c + oo*I))" ) assert inverse_fourier_transform(f(s), s, x).rewrite("Integral") == Integral( f(s) * exp(2 * I * pi * s * x), (s, -oo, oo) )
def set_viscoelastic_bendingmod(self): """Construct time-dependent function viscoelastic (time-dependent) bending modulus by taking inverse Laplace transform of laplace_transformed_D. t0: time at which to evaluate""" s = Symbol('s') #Laplace variable s, to be used in SymPy computation t = Symbol('t', positive=True) laml = Symbol('laml', positive=True) #stand-in symbol for lame_lambda m = Symbol('m', positive=True) #stand-in symbol for shearmod tr = Symbol('tr', positive=True) #stand-in symbol for t_relax h = Symbol('h', positive=True) #stand-in symbol for thickness lambda_bar = laml + (2 * m / (3 * (1 + tr * s))) #transformed Lame lambda mu_bar = (tr * s / (1 + tr * s)) * m #transformed Lame mu (shear mod) #self.lambda_bar = lambda_bar #self.mu_bar = mu_bar youngmod_bar = 2 * mu_bar + (mu_bar * lambda_bar / (mu_bar + lambda_bar)) poisson_bar = lambda_bar / (2 * (mu_bar + lambda_bar)) bending_mod_bar = youngmod_bar * h**3 / (12 * (1 - poisson_bar**2)) symbolic_ve_D = inverse_laplace_transform( bending_mod_bar / s, s, t ) #construct viscoelastic D(t) through SymPy inverse Laplace transform self.symbolic_ve_D = lambda t0: symbolic_ve_D.subs( ((laml, self.lame_lambda), (m, self.shearmod), (tr, self.t_relax), (h, self.thickness), (t, t0)))
def test_expint(): from sympy.functions.elementary.miscellaneous import Max from sympy.functions.special.error_functions import (Ci, E1, Ei, Si) from sympy.functions.special.zeta_functions import lerchphi from sympy.simplify.simplify import simplify aneg = Symbol('a', negative=True) u = Symbol('u', polar=True) assert mellin_transform(E1(x), x, s) == (gamma(s)/s, (0, oo), True) assert inverse_mellin_transform(gamma(s)/s, s, x, (0, oo)).rewrite(expint).expand() == E1(x) assert mellin_transform(expint(a, x), x, s) == \ (gamma(s)/(a + s - 1), (Max(1 - re(a), 0), oo), True) # XXX IMT has hickups with complicated strips ... assert simplify(unpolarify( inverse_mellin_transform(gamma(s)/(aneg + s - 1), s, x, (1 - aneg, oo)).rewrite(expint).expand(func=True))) == \ expint(aneg, x) assert mellin_transform(Si(x), x, s) == \ (-2**s*sqrt(pi)*gamma(s/2 + S.Half)/( 2*s*gamma(-s/2 + 1)), (-1, 0), True) assert inverse_mellin_transform(-2**s*sqrt(pi)*gamma((s + 1)/2) /(2*s*gamma(-s/2 + 1)), s, x, (-1, 0)) \ == Si(x) assert mellin_transform(Ci(sqrt(x)), x, s) == \ (-2**(2*s - 1)*sqrt(pi)*gamma(s)/(s*gamma(-s + S.Half)), (0, 1), True) assert inverse_mellin_transform( -4**s*sqrt(pi)*gamma(s)/(2*s*gamma(-s + S.Half)), s, u, (0, 1)).expand() == Ci(sqrt(u)) # TODO LT of Si, Shi, Chi is a mess ... assert laplace_transform(Ci(x), x, s) == (-log(1 + s**2)/2/s, 0, True) assert laplace_transform(expint(a, x), x, s) == \ (lerchphi(s*exp_polar(I*pi), 1, a), 0, re(a) > S.Zero) assert laplace_transform(expint(1, x), x, s) == (log(s + 1)/s, 0, True) assert laplace_transform(expint(2, x), x, s) == \ ((s - log(s + 1))/s**2, 0, True) assert inverse_laplace_transform(-log(1 + s**2)/2/s, s, u).expand() == \ Heaviside(u)*Ci(u) assert inverse_laplace_transform(log(s + 1)/s, s, x).rewrite(expint) == \ Heaviside(x)*E1(x) assert inverse_laplace_transform((s - log(s + 1))/s**2, s, x).rewrite(expint).expand() == \ (expint(2, x)*Heaviside(x)).rewrite(Ei).rewrite(expint).expand()
def test_expint(): from sympy import E1, expint, Max, re, lerchphi, Symbol, simplify, Si, Ci, Ei aneg = Symbol("a", negative=True) u = Symbol("u", polar=True) assert mellin_transform(E1(x), x, s) == (gamma(s) / s, (0, oo), True) assert inverse_mellin_transform(gamma(s) / s, s, x, (0, oo)).rewrite(expint).expand() == E1(x) assert mellin_transform(expint(a, x), x, s) == (gamma(s) / (a + s - 1), (Max(1 - re(a), 0), oo), True) # XXX IMT has hickups with complicated strips ... assert simplify( unpolarify( inverse_mellin_transform(gamma(s) / (aneg + s - 1), s, x, (1 - aneg, oo)).rewrite(expint).expand(func=True) ) ) == expint(aneg, x) assert mellin_transform(Si(x), x, s) == ( -2 ** s * sqrt(pi) * gamma(s / 2 + S(1) / 2) / (2 * s * gamma(-s / 2 + 1)), (-1, 0), True, ) assert inverse_mellin_transform( -2 ** s * sqrt(pi) * gamma((s + 1) / 2) / (2 * s * gamma(-s / 2 + 1)), s, x, (-1, 0) ) == Si(x) assert mellin_transform(Ci(sqrt(x)), x, s) == ( -2 ** (2 * s - 1) * sqrt(pi) * gamma(s) / (s * gamma(-s + S(1) / 2)), (0, 1), True, ) assert inverse_mellin_transform( -4 ** s * sqrt(pi) * gamma(s) / (2 * s * gamma(-s + S(1) / 2)), s, u, (0, 1) ).expand() == Ci(sqrt(u)) # TODO LT of Si, Shi, Chi is a mess ... assert laplace_transform(Ci(x), x, s) == (-log(1 + s ** 2) / 2 / s, 0, True) assert laplace_transform(expint(a, x), x, s) == (lerchphi(s * polar_lift(-1), 1, a), 0, S(0) < re(a)) assert laplace_transform(expint(1, x), x, s) == (log(s + 1) / s, 0, True) assert laplace_transform(expint(2, x), x, s) == ((s - log(s + 1)) / s ** 2, 0, True) assert inverse_laplace_transform(-log(1 + s ** 2) / 2 / s, s, u).expand() == Heaviside(u) * Ci(u) assert inverse_laplace_transform(log(s + 1) / s, s, x).rewrite(expint) == Heaviside(x) * E1(x) assert ( inverse_laplace_transform((s - log(s + 1)) / s ** 2, s, x).rewrite(expint).expand() == (expint(2, x) * Heaviside(x)).rewrite(Ei).rewrite(expint).expand() )
def test_laplace_transform(): LT = laplace_transform a, b, c, = symbols('a b c', positive=True) t = symbols('t') w = Symbol("w") f = Function("f") # Test unevaluated form assert laplace_transform(f(t), t, w) == LaplaceTransform(f(t), t, w) assert inverse_laplace_transform(f(w), w, t, plane=0) == InverseLaplaceTransform( f(w), w, t, 0) # test a bug spos = symbols('s', positive=True) assert LT(exp(t), t, spos)[:2] == (1 / (spos - 1), True) # basic tests from wikipedia assert LT((t-a)**b*exp(-c*(t-a))*Heaviside(t-a), t, s) \ == ((s + c)**(-b - 1)*exp(-a*s)*gamma(b + 1), -c, True) assert LT(t**a, t, s) == (s**(-a - 1) * gamma(a + 1), 0, True) assert LT(Heaviside(t), t, s) == (1 / s, 0, True) assert LT(Heaviside(t - a), t, s) == (exp(-a * s) / s, 0, True) assert LT(1 - exp(-a * t), t, s) == (a / (s * (a + s)), 0, True) assert LT((exp(2*t)-1)*exp(-b - t)*Heaviside(t)/2, t, s, noconds=True) \ == exp(-b)/(s**2 - 1) assert LT(exp(t), t, s)[:2] == (1 / (s - 1), 1) assert LT(exp(2 * t), t, s)[:2] == (1 / (s - 2), 2) assert LT(exp(a * t), t, s)[:2] == (1 / (s - a), a) assert LT(log(t / a), t, s) == ((log(a) + log(s) + EulerGamma) / (-s), 0, True) assert LT(erf(t), t, s) == ((-erf(s / 2) + 1) * exp(s**2 / 4) / s, 0, True) assert LT(sin(a * t), t, s) == (a / (a**2 + s**2), 0, True) assert LT(cos(a * t), t, s) == (s / (a**2 + s**2), 0, True) # TODO would be nice to have these come out better assert LT(exp(-a * t) * sin(b * t), t, s) == (1 / b / (1 + (a + s)**2 / b**2), -a, True) assert LT(exp(-a*t)*cos(b*t), t, s) == \ (1/(s + a)/(1 + b**2/(a + s)**2), -a, True) # TODO sinh, cosh have delicate cancellation assert LT(besselj(0, t), t, s) == (1 / sqrt(1 + s**2), 0, True) assert LT(besselj(1, t), t, s) == (1 - 1 / sqrt(1 + 1 / s**2), 0, True) # TODO general order works, but is a *mess* # TODO besseli also works, but is an even greater mess # test a bug in conditions processing # TODO the auxiliary condition should be recognised/simplified assert LT(exp(t) * cos(t), t, s)[:-1] in [ ((s - 1) / (s**2 - 2 * s + 2), -oo), ((s - 1) / ((s - 1)**2 + 1), -oo), ]
def test_expint(): from sympy import E1, expint, Max, re, lerchphi, Symbol, simplify, Si, Ci, Ei aneg = Symbol('a', negative=True) u = Symbol('u', polar=True) assert mellin_transform(E1(x), x, s) == (gamma(s) / s, (0, oo), True) assert inverse_mellin_transform(gamma(s) / s, s, x, (0, oo)).rewrite(expint).expand() == E1(x) assert mellin_transform(expint(a, x), x, s) == \ (gamma(s)/(a + s - 1), (Max(1 - re(a), 0), oo), True) # XXX IMT has hickups with complicated strips ... assert simplify(unpolarify( inverse_mellin_transform(gamma(s)/(aneg + s - 1), s, x, (1 - aneg, oo)).rewrite(expint).expand(func=True))) == \ expint(aneg, x) assert mellin_transform(Si(x), x, s) == \ (-2**s*sqrt(pi)*gamma(s/2 + S(1)/2)/( 2*s*gamma(-s/2 + 1)), (-1, 0), True) assert inverse_mellin_transform(-2**s*sqrt(pi)*gamma((s + 1)/2) /(2*s*gamma(-s/2 + 1)), s, x, (-1, 0)) \ == Si(x) assert mellin_transform(Ci(sqrt(x)), x, s) == \ (-2**(2*s - 1)*sqrt(pi)*gamma(s)/(s*gamma(-s + S(1)/2)), (0, 1), True) assert inverse_mellin_transform( -4**s * sqrt(pi) * gamma(s) / (2 * s * gamma(-s + S(1) / 2)), s, u, (0, 1)).expand() == Ci(sqrt(u)) # TODO LT of Si, Shi, Chi is a mess ... assert laplace_transform(Ci(x), x, s) == (-log(1 + s**2) / 2 / s, 0, True) assert laplace_transform(expint(a, x), x, s) == \ (lerchphi(s*polar_lift(-1), 1, a), 0, S(0) < re(a)) assert laplace_transform(expint(1, x), x, s) == (log(s + 1) / s, 0, True) assert laplace_transform(expint(2, x), x, s) == \ ((s - log(s + 1))/s**2, 0, True) assert inverse_laplace_transform(-log(1 + s**2)/2/s, s, u).expand() == \ Heaviside(u)*Ci(u) assert inverse_laplace_transform(log(s + 1)/s, s, x).rewrite(expint) == \ Heaviside(x)*E1(x) assert inverse_laplace_transform((s - log(s + 1))/s**2, s, x).rewrite(expint).expand() == \ (expint(2, x)*Heaviside(x)).rewrite(Ei).rewrite(expint).expand()
def inverse_laplace_sympy(expr, s, t): # This barfs when needing to generate Dirac deltas from sympy.integrals.transforms import inverse_laplace_transform result = inverse_laplace_transform(expr, t, s) if result.has(sym.InverseLaplaceTransform): raise ValueError('Cannot determine inverse Laplace' ' transform of %s with sympy' % expr) return result
def test_laplace_transform(): LT = laplace_transform a, b, c, = symbols('a b c', positive=True) t = symbols('t') w = Symbol("w") f = Function("f") # Test unevaluated form assert laplace_transform(f(t), t, w) == LaplaceTransform(f(t), t, w) assert inverse_laplace_transform(f(w), w, t, plane=0) == InverseLaplaceTransform(f(w), w, t, 0) # test a bug spos = symbols('s', positive=True) assert LT(exp(t), t, spos)[:2] == (1/(spos - 1), True) # basic tests from wikipedia assert LT((t-a)**b*exp(-c*(t-a))*Heaviside(t-a), t, s) \ == ((s + c)**(-b - 1)*exp(-a*s)*gamma(b + 1), -c, True) assert LT(t**a, t, s) == (s**(-a - 1)*gamma(a + 1), 0, True) assert LT(Heaviside(t), t, s) == (1/s, 0, True) assert LT(Heaviside(t - a), t, s) == (exp(-a*s)/s, 0, True) assert LT(1 - exp(-a*t), t, s) == (a/(s*(a + s)), 0, True) assert LT((exp(2*t)-1)*exp(-b - t)*Heaviside(t)/2, t, s, noconds=True) \ == exp(-b)/(s**2 - 1) assert LT(exp(t), t, s)[:2] == (1/(s-1), 1) assert LT(exp(2*t), t, s)[:2] == (1/(s-2), 2) assert LT(exp(a*t), t, s)[:2] == (1/(s-a), a) assert LT(log(t/a), t, s) == ((log(a) + log(s) + EulerGamma)/(-s), 0, True) assert LT(erf(t), t, s) == ((-erf(s/2) + 1)*exp(s**2/4)/s, 0, True) assert LT(sin(a*t), t, s) == (a/(a**2 + s**2), 0, True) assert LT(cos(a*t), t, s) == (s/(a**2 + s**2), 0, True) # TODO would be nice to have these come out better assert LT(exp(-a*t)*sin(b*t), t, s) == (1/b/(1 + (a + s)**2/b**2), -a, True) assert LT(exp(-a*t)*cos(b*t), t, s) == \ (1/(s + a)/(1 + b**2/(a + s)**2), -a, True) # TODO sinh, cosh have delicate cancellation assert LT(besselj(0, t), t, s) == (1/sqrt(1 + s**2), 0, True) assert LT(besselj(1, t), t, s) == (1 - 1/sqrt(1 + 1/s**2), 0, True) # TODO general order works, but is a *mess* # TODO besseli also works, but is an even greater mess # test a bug in conditions processing # TODO the auxiliary condition should be recognised/simplified assert LT(exp(t)*cos(t), t, s)[:-1] in [ ((s - 1)/(s**2 - 2*s + 2), -oo), ((s - 1)/((s - 1)**2 + 1), -oo), ]
def sympy(self, expr, s, t): self.debug('Resorting to SymPy') # This barfs when needing to generate Dirac deltas from sympy.integrals.transforms import inverse_laplace_transform result = inverse_laplace_transform(expr, s, t) if result.has(sym.InverseLaplaceTransform): self.error('SymPy does not know either') return result
def transfer_to_differential(tf, fun_X=Function('X'), fun_F=Function('F')): tf = fraction(tf) res = Eq(inverse_laplace_transform(tf[1] * fun_X(s), s, t), inverse_laplace_transform(tf[0] * fun_F(s), s, t)) wf = Wild('w') ilw = InverseLaplaceTransform(wf, s, t, None) for exp in res.find(ilw): e = exp.match(ilw)[wf] args = e.args if len(args) == 2: p = 1 if not isinstance(args[0], Pow) else args[0].args[1] newexp = Derivative(Function(args[1].name.lower())(t), t, p) res = res.replace(exp, newexp) elif len(args) == 1: newexp = Function(e.name.lower())(t) res = res.replace(exp, newexp) return res
def test_issue_8514(): from sympy import simplify a, b, c, = symbols('a b c', positive=True) t = symbols('t', positive=True) ft = simplify(inverse_laplace_transform(1/(a*s**2+b*s+c),s, t)) assert ft == ((exp(t*(exp(I*atan2(0, -4*a*c + b**2)/2) - exp(-I*atan2(0, -4*a*c + b**2)/2))* sqrt(Abs(4*a*c - b**2))/(4*a))*exp(t*cos(atan2(0, -4*a*c + b**2)/2) *sqrt(Abs(4*a*c - b**2))/a) + I*sin(t*sin(atan2(0, -4*a*c + b**2)/2) *sqrt(Abs(4*a*c - b**2))/(2*a)) - cos(t*sin(atan2(0, -4*a*c + b**2)/2) *sqrt(Abs(4*a*c - b**2))/(2*a)))*exp(-t*(b + cos(atan2(0, -4*a*c + b**2)/2) *sqrt(Abs(4*a*c - b**2)))/(2*a))/sqrt(-4*a*c + b**2))
def ILT(expr, s, t, **assumptions): """Calculate inverse Laplace transform of X(s) and return x(t). The unilateral Laplace transform cannot determine x(t) for t < 0 unless given additional information in the way of assumptions. The assumptions are: dc -- x(t) = constant so X(s) must have the form constant / s causal -- x(t) = 0 for t < 0. ac -- x(t) = A cos(a * t) + B * sin(b * t) """ return inverse_laplace_transform(expr, s, t, **assumptions)
def test_as_integral(): from sympy import Integral f = Function('f') assert mellin_transform(f(x), x, s).rewrite('Integral') == \ Integral(x**(s - 1)*f(x), (x, 0, oo)) assert fourier_transform(f(x), x, s).rewrite('Integral') == \ Integral(f(x)*exp(-2*I*pi*s*x), (x, -oo, oo)) assert laplace_transform(f(x), x, s).rewrite('Integral') == \ Integral(f(x)*exp(-s*x), (x, 0, oo)) assert str(2*pi*I*inverse_mellin_transform(f(s), s, x, (a, b)).rewrite('Integral')) \ == "Integral(f(s)/x**s, (s, _c - oo*I, _c + oo*I))" assert str(2*pi*I*inverse_laplace_transform(f(s), s, x).rewrite('Integral')) == \ "Integral(f(s)*exp(s*x), (s, _c - oo*I, _c + oo*I))" assert inverse_fourier_transform(f(s), s, x).rewrite('Integral') == \ Integral(f(s)*exp(2*I*pi*s*x), (s, -oo, oo))
def test_as_integral(): from sympy import Function, Integral f = Function('f') assert mellin_transform(f(x), x, s).rewrite('Integral') == \ Integral(x**(s - 1)*f(x), (x, 0, oo)) assert fourier_transform(f(x), x, s).rewrite('Integral') == \ Integral(f(x)*exp(-2*I*pi*s*x), (x, -oo, oo)) assert laplace_transform(f(x), x, s).rewrite('Integral') == \ Integral(f(x)*exp(-s*x), (x, 0, oo)) assert str(inverse_mellin_transform(f(s), s, x, (a, b)).rewrite('Integral')) \ == "Integral(x**(-s)*f(s), (s, _c - oo*I, _c + oo*I))" assert str(inverse_laplace_transform(f(s), s, x).rewrite('Integral')) == \ "Integral(f(s)*exp(s*x), (s, _c - oo*I, _c + oo*I))" assert inverse_fourier_transform(f(s), s, x).rewrite('Integral') == \ Integral(f(s)*exp(2*I*pi*s*x), (s, -oo, oo))
def alap(n): from sympy.integrals.transforms import inverse_laplace_transform from sympy import separatevars import sympy from sympy import simplify from sympy.parsing.sympy_parser import parse_expr x = sympy.Symbol("s", real=True) f = parse_expr(n) f = f.subs({parse_expr("s"): x}) f = inverse_laplace_transform(f, x, 't') f = separatevars(f, force=True) #print(f) f = simplify(f, measure=my_measure1, ratio=10) return str(f)
def inverse_laplace(self): """Attempt inverse Laplace transform""" try: result = self._inverse_laplace() except: print('Determining inverse Laplace transform with sympy...') # Try splitting into partial fractions to help sympy. expr = self.partfrac().expr # This barfs when needing to generate Dirac deltas from sympy.integrals.transforms import inverse_laplace_transform result = inverse_laplace_transform(expr, t, self.var) if hasattr(self, '_laplace_conjugate_class'): result = self._laplace_conjugate_class(result) return result
def test_laplace_transform(): from sympy import fresnels, fresnelc LT = laplace_transform a, b, c, = symbols('a b c', positive=True) t = symbols('t') w = Symbol("w") f = Function("f") # Test unevaluated form assert laplace_transform(f(t), t, w) == LaplaceTransform(f(t), t, w) assert inverse_laplace_transform(f(w), w, t, plane=0) == InverseLaplaceTransform( f(w), w, t, 0) # test a bug spos = symbols('s', positive=True) assert LT(exp(t), t, spos)[:2] == (1 / (spos - 1), True) # basic tests from wikipedia assert LT((t - a)**b*exp(-c*(t - a))*Heaviside(t - a), t, s) == \ ((s + c)**(-b - 1)*exp(-a*s)*gamma(b + 1), -c, True) assert LT(t**a, t, s) == (s**(-a - 1) * gamma(a + 1), 0, True) assert LT(Heaviside(t), t, s) == (1 / s, 0, True) assert LT(Heaviside(t - a), t, s) == (exp(-a * s) / s, 0, True) assert LT(1 - exp(-a * t), t, s) == (a / (s * (a + s)), 0, True) assert LT((exp(2*t) - 1)*exp(-b - t)*Heaviside(t)/2, t, s, noconds=True) \ == exp(-b)/(s**2 - 1) assert LT(exp(t), t, s)[:2] == (1 / (s - 1), 1) assert LT(exp(2 * t), t, s)[:2] == (1 / (s - 2), 2) assert LT(exp(a * t), t, s)[:2] == (1 / (s - a), a) assert LT(log(t / a), t, s) == ((log(a * s) + EulerGamma) / s / -1, 0, True) assert LT(erf(t), t, s) == ((erfc(s / 2)) * exp(s**2 / 4) / s, 0, True) assert LT(sin(a * t), t, s) == (a / (a**2 + s**2), 0, True) assert LT(cos(a * t), t, s) == (s / (a**2 + s**2), 0, True) # TODO would be nice to have these come out better assert LT(exp(-a * t) * sin(b * t), t, s) == (b / (b**2 + (a + s)**2), -a, True) assert LT(exp(-a*t)*cos(b*t), t, s) == \ ((a + s)/(b**2 + (a + s)**2), -a, True) assert LT(besselj(0, t), t, s) == (1 / sqrt(1 + s**2), 0, True) assert LT(besselj(1, t), t, s) == (1 - 1 / sqrt(1 + 1 / s**2), 0, True) # TODO general order works, but is a *mess* # TODO besseli also works, but is an even greater mess # test a bug in conditions processing # TODO the auxiliary condition should be recognised/simplified assert LT(exp(t) * cos(t), t, s)[:-1] in [ ((s - 1) / (s**2 - 2 * s + 2), -oo), ((s - 1) / ((s - 1)**2 + 1), -oo), ] # Fresnel functions assert laplace_transform(fresnels(t), t, s) == \ ((-sin(s**2/(2*pi))*fresnels(s/pi) + sin(s**2/(2*pi))/2 - cos(s**2/(2*pi))*fresnelc(s/pi) + cos(s**2/(2*pi))/2)/s, 0, True) assert laplace_transform( fresnelc(t), t, s) == (((2 * sin(s**2 / (2 * pi)) * fresnelc(s / pi) - 2 * cos(s**2 / (2 * pi)) * fresnels(s / pi) + sqrt(2) * cos(s**2 / (2 * pi) + pi / 4)) / (2 * s), 0, True)) assert LT(Matrix([[exp(t), t*exp(-t)], [t*exp(-t), exp(t)]]), t, s) ==\ Matrix([ [(1/(s - 1), 1, True), ((s + 1)**(-2), 0, True)], [((s + 1)**(-2), 0, True), (1/(s - 1), 1, True)] ])
@author: CatOnTour """ import mpmath as mp import numpy as np import matplotlib.pyplot as plt from sympy.abc import s from sympy.integrals.transforms import inverse_laplace_transform from sympy import symbols, lambdify # analytic f_sdomain = s / (s - 1) time = symbols('time', positive=True, real=True) f_tdomain = inverse_laplace_transform(f_sdomain, s, time) f_tdomain_func = lambdify(time, f_tdomain) # numerical def f(s): return 100 / (s**2 + 0.5 * s + 2) t = np.linspace(0.01, 20, 100) G = [] for i in t: G.append(mp.invertlaplace(f, i, method='dehoog', dps=10, degree=18))
#print Input_func_laplace[0] #transfer func as given in paper Trans_func = k*((tau_p*s+1)/(tau_d*s+1)) Output_func_laplace = Input_func_laplace[0]*Trans_func print Output_func_laplace '''c=[] plt.figure(3) for i in range(0,25): c.append(Output_func_laplace.subs(s,ti[i])) plt.plot(ti,c) plt.title('Laplace Function curve') plt.show()''' Inv_laplace = inverse_laplace_transform(Output_func_laplace,s,t) print Inv_laplace #Output_func = Inv_laplace #plotting output function plt.figure(2) b=[] for i in range(0,25): b.append(Inv_laplace.subs(t,ti[i])) plt.plot(ti,b) plt.title('Output Function') plt.xlabel('Time(t)') #plt.ylabel('') plt.show()
# coding: utf-8 # 참고문헌: http://docs.sympy.org/dev/modules/integrals/integrals.html#sympy.integrals.transforms.laplace_transform # http://www.mathalino.com/reviewer/advance-engineering-mathematics/table-laplace-transforms-elementary-functions import sympy as sp from sympy.integrals.transforms import inverse_laplace_transform from sympy.integrals.transforms import laplace_transform t, s = sp.symbols('t s') w = sp.Symbol('w', real=True) a = sp.Symbol('a', real=True) p = sp.Symbol('p', real=True) y = a * sp.sin(w * t + p) print("y = %s" % y) Y = laplace_transform(y, t, s) print("Y = %s" % str(Y)) yi = inverse_laplace_transform(Y[0], s, t) print("yi = %s" % str(yi))
def test_laplace_transform(): from sympy import lowergamma from sympy.functions.special.delta_functions import DiracDelta from sympy.functions.special.error_functions import (fresnelc, fresnels) LT = laplace_transform a, b, c, = symbols('a, b, c', positive=True) t, w, x = symbols('t, w, x') f = Function("f") g = Function("g") # Test rule-base evaluation according to # http://eqworld.ipmnet.ru/en/auxiliary/inttrans/ # Power-law functions (laplace2.pdf) assert LT(a*t+t**2+t**(S(5)/2), t, s) ==\ (a/s**2 + 2/s**3 + 15*sqrt(pi)/(8*s**(S(7)/2)), 0, True) assert LT(b/(t+a), t, s) == (-b*exp(-a*s)*Ei(-a*s), 0, True) assert LT(1/sqrt(t+a), t, s) ==\ (sqrt(pi)*sqrt(1/s)*exp(a*s)*erfc(sqrt(a)*sqrt(s)), 0, True) assert LT(sqrt(t)/(t+a), t, s) ==\ (-pi*sqrt(a)*exp(a*s)*erfc(sqrt(a)*sqrt(s)) + sqrt(pi)*sqrt(1/s), 0, True) assert LT((t+a)**(-S(3)/2), t, s) ==\ (-2*sqrt(pi)*sqrt(s)*exp(a*s)*erfc(sqrt(a)*sqrt(s)) + 2/sqrt(a), 0, True) assert LT(t**(S(1)/2)*(t+a)**(-1), t, s) ==\ (-pi*sqrt(a)*exp(a*s)*erfc(sqrt(a)*sqrt(s)) + sqrt(pi)*sqrt(1/s), 0, True) assert LT(1/(a*sqrt(t) + t**(3/2)), t, s) ==\ (pi*sqrt(a)*exp(a*s)*erfc(sqrt(a)*sqrt(s)), 0, True) assert LT((t+a)**b, t, s) ==\ (s**(-b - 1)*exp(-a*s)*lowergamma(b + 1, a*s), 0, True) assert LT(t**5/(t+a), t, s) == (120*a**5*lowergamma(-5, a*s), 0, True) # Exponential functions (laplace3.pdf) assert LT(exp(t), t, s) == (1/(s - 1), 1, True) assert LT(exp(2*t), t, s) == (1/(s - 2), 2, True) assert LT(exp(a*t), t, s) == (1/(s - a), a, True) assert LT(exp(a*(t-b)), t, s) == (exp(-a*b)/(-a + s), a, True) assert LT(t*exp(-a*(t)), t, s) == ((a + s)**(-2), -a, True) assert LT(t*exp(-a*(t-b)), t, s) == (exp(a*b)/(a + s)**2, -a, True) assert LT(b*t*exp(-a*t), t, s) == (b/(a + s)**2, -a, True) assert LT(t**(S(7)/4)*exp(-8*t)/gamma(S(11)/4), t, s) ==\ ((s + 8)**(-S(11)/4), -8, True) assert LT(t**(S(3)/2)*exp(-8*t), t, s) ==\ (3*sqrt(pi)/(4*(s + 8)**(S(5)/2)), -8, True) assert LT(t**a*exp(-a*t), t, s) == ((a+s)**(-a-1)*gamma(a+1), -a, True) assert LT(b*exp(-a*t**2), t, s) ==\ (sqrt(pi)*b*exp(s**2/(4*a))*erfc(s/(2*sqrt(a)))/(2*sqrt(a)), 0, True) assert LT(exp(-2*t**2), t, s) ==\ (sqrt(2)*sqrt(pi)*exp(s**2/8)*erfc(sqrt(2)*s/4)/4, 0, True) assert LT(b*exp(2*t**2), t, s) == b*LaplaceTransform(exp(2*t**2), t, s) assert LT(t*exp(-a*t**2), t, s) ==\ (1/(2*a) - s*erfc(s/(2*sqrt(a)))/(4*sqrt(pi)*a**(S(3)/2)), 0, True) assert LT(exp(-a/t), t, s) ==\ (2*sqrt(a)*sqrt(1/s)*besselk(1, 2*sqrt(a)*sqrt(s)), 0, True) assert LT(sqrt(t)*exp(-a/t), t, s) ==\ (sqrt(pi)*(2*sqrt(a)*sqrt(s) + 1)*sqrt(s**(-3))*exp(-2*sqrt(a)*\ sqrt(s))/2, 0, True) assert LT(exp(-a/t)/sqrt(t), t, s) ==\ (sqrt(pi)*sqrt(1/s)*exp(-2*sqrt(a)*sqrt(s)), 0, True) assert LT( exp(-a/t)/(t*sqrt(t)), t, s) ==\ (sqrt(pi)*sqrt(1/a)*exp(-2*sqrt(a)*sqrt(s)), 0, True) assert LT(exp(-2*sqrt(a*t)), t, s) ==\ ( 1/s -sqrt(pi)*sqrt(a) * exp(a/s)*erfc(sqrt(a)*sqrt(1/s))/\ s**(S(3)/2), 0, True) assert LT(exp(-2*sqrt(a*t))/sqrt(t), t, s) == (exp(a/s)*erfc(sqrt(a)*\ sqrt(1/s))*(sqrt(pi)*sqrt(1/s)), 0, True) assert LT(t**4*exp(-2/t), t, s) ==\ (8*sqrt(2)*(1/s)**(S(5)/2)*besselk(5, 2*sqrt(2)*sqrt(s)), 0, True) # Hyperbolic functions (laplace4.pdf) assert LT(sinh(a*t), t, s) == (a/(-a**2 + s**2), a, True) assert LT(b*sinh(a*t)**2, t, s) == (2*a**2*b/(-4*a**2*s**2 + s**3), 2*a, True) # The following line confirms that issue #21202 is solved assert LT(cosh(2*t), t, s) == (s/(-4 + s**2), 2, True) assert LT(cosh(a*t), t, s) == (s/(-a**2 + s**2), a, True) assert LT(cosh(a*t)**2, t, s) == ((-2*a**2 + s**2)/(-4*a**2*s**2 + s**3), 2*a, True) assert LT(sinh(x + 3), x, s) == ( (-s + (s + 1)*exp(6) + 1)*exp(-3)/(s - 1)/(s + 1)/2, 0, Abs(s) > 1) # The following line replaces the old test test_issue_7173() assert LT(sinh(a*t)*cosh(a*t), t, s) == (a/(-4*a**2 + s**2), 2*a, True) assert LT(sinh(a*t)/t, t, s) == (log((a + s)/(-a + s))/2, a, True) assert LT(t**(-S(3)/2)*sinh(a*t), t, s) ==\ (-sqrt(pi)*(sqrt(-a + s) - sqrt(a + s)), a, True) assert LT(sinh(2*sqrt(a*t)), t, s) ==\ (sqrt(pi)*sqrt(a)*exp(a/s)/s**(S(3)/2), 0, True) assert LT(sqrt(t)*sinh(2*sqrt(a*t)), t, s) ==\ (-sqrt(a)/s**2 + sqrt(pi)*(a + s/2)*exp(a/s)*erf(sqrt(a)*\ sqrt(1/s))/s**(S(5)/2), 0, True) assert LT(sinh(2*sqrt(a*t))/sqrt(t), t, s) ==\ (sqrt(pi)*exp(a/s)*erf(sqrt(a)*sqrt(1/s))/sqrt(s), 0, True) assert LT(sinh(sqrt(a*t))**2/sqrt(t), t, s) ==\ (sqrt(pi)*(exp(a/s) - 1)/(2*sqrt(s)), 0, True) assert LT(t**(S(3)/7)*cosh(a*t), t, s) ==\ (((a + s)**(-S(10)/7) + (-a+s)**(-S(10)/7))*gamma(S(10)/7)/2, a, True) assert LT(cosh(2*sqrt(a*t)), t, s) ==\ (sqrt(pi)*sqrt(a)*exp(a/s)*erf(sqrt(a)*sqrt(1/s))/s**(S(3)/2) + 1/s, 0, True) assert LT(sqrt(t)*cosh(2*sqrt(a*t)), t, s) ==\ (sqrt(pi)*(a + s/2)*exp(a/s)/s**(S(5)/2), 0, True) assert LT(cosh(2*sqrt(a*t))/sqrt(t), t, s) ==\ (sqrt(pi)*exp(a/s)/sqrt(s), 0, True) assert LT(cosh(sqrt(a*t))**2/sqrt(t), t, s) ==\ (sqrt(pi)*(exp(a/s) + 1)/(2*sqrt(s)), 0, True) # logarithmic functions (laplace5.pdf) assert LT(log(t), t, s) == (-log(s+S.EulerGamma)/s, 0, True) assert LT(log(t/a), t, s) == (-log(a*s + S.EulerGamma)/s, 0, True) assert LT(log(1+a*t), t, s) == (-exp(s/a)*Ei(-s/a)/s, 0, True) assert LT(log(t+a), t, s) == ((log(a) - exp(s/a)*Ei(-s/a)/s)/s, 0, True) assert LT(log(t)/sqrt(t), t, s) ==\ (sqrt(pi)*(-log(s) - 2*log(2) - S.EulerGamma)/sqrt(s), 0, True) assert LT(t**(S(5)/2)*log(t), t, s) ==\ (15*sqrt(pi)*(-log(s)-2*log(2)-S.EulerGamma+S(46)/15)/(8*s**(S(7)/2)), 0, True) assert (LT(t**3*log(t), t, s, noconds=True)-6*(-log(s) - S.EulerGamma\ + S(11)/6)/s**4).simplify() == S.Zero assert LT(log(t)**2, t, s) ==\ (((log(s) + EulerGamma)**2 + pi**2/6)/s, 0, True) assert LT(exp(-a*t)*log(t), t, s) ==\ ((-log(a + s) - S.EulerGamma)/(a + s), -a, True) # Trigonometric functions (laplace6.pdf) assert LT(sin(a*t), t, s) == (a/(a**2 + s**2), 0, True) assert LT(Abs(sin(a*t)), t, s) ==\ (a*coth(pi*s/(2*a))/(a**2 + s**2), 0, True) assert LT(sin(a*t)/t, t, s) == (atan(a/s), 0, True) assert LT(sin(a*t)**2/t, t, s) == (log(4*a**2/s**2 + 1)/4, 0, True) assert LT(sin(a*t)**2/t**2, t, s) ==\ (a*atan(2*a/s) - s*log(4*a**2/s**2 + 1)/4, 0, True) assert LT(sin(2*sqrt(a*t)), t, s) ==\ (sqrt(pi)*sqrt(a)*exp(-a/s)/s**(S(3)/2), 0, True) assert LT(sin(2*sqrt(a*t))/t, t, s) == (pi*erf(sqrt(a)*sqrt(1/s)), 0, True) assert LT(cos(a*t), t, s) == (s/(a**2 + s**2), 0, True) assert LT(cos(a*t)**2, t, s) ==\ ((2*a**2 + s**2)/(s*(4*a**2 + s**2)), 0, True) assert LT(sqrt(t)*cos(2*sqrt(a*t)), t, s) ==\ (sqrt(pi)*(-2*a + s)*exp(-a/s)/(2*s**(S(5)/2)), 0, True) assert LT(cos(2*sqrt(a*t))/sqrt(t), t, s) ==\ (sqrt(pi)*sqrt(1/s)*exp(-a/s), 0, True) assert LT(sin(a*t)*sin(b*t), t, s) ==\ (2*a*b*s/((s**2 + (a - b)**2)*(s**2 + (a + b)**2)), 0, True) assert LT(cos(a*t)*sin(b*t), t, s) ==\ (b*(-a**2 + b**2 + s**2)/((s**2 + (a - b)**2)*(s**2 + (a + b)**2)), 0, True) assert LT(cos(a*t)*cos(b*t), t, s) ==\ (s*(a**2 + b**2 + s**2)/((s**2 + (a - b)**2)*(s**2 + (a + b)**2)), 0, True) assert LT(c*exp(-b*t)*sin(a*t), t, s) == (a*c/(a**2 + (b + s)**2), -b, True) assert LT(c*exp(-b*t)*cos(a*t), t, s) == ((b + s)*c/(a**2 + (b + s)**2), -b, True) assert LT(cos(x + 3), x, s) == ((s*cos(3) - sin(3))/(s**2 + 1), 0, True) # Error functions (laplace7.pdf) assert LT(erf(a*t), t, s) == (exp(s**2/(4*a**2))*erfc(s/(2*a))/s, 0, True) assert LT(erf(sqrt(a*t)), t, s) == (sqrt(a)/(s*sqrt(a + s)), 0, True) assert LT(exp(a*t)*erf(sqrt(a*t)), t, s) ==\ (sqrt(a)/(sqrt(s)*(-a + s)), a, True) assert LT(erf(sqrt(a/t)/2), t, s) == ((1-exp(-sqrt(a)*sqrt(s)))/s, 0, True) assert LT(erfc(sqrt(a*t)), t, s) ==\ ((-sqrt(a) + sqrt(a + s))/(s*sqrt(a + s)), 0, True) assert LT(exp(a*t)*erfc(sqrt(a*t)), t, s) ==\ (1/(sqrt(a)*sqrt(s) + s), 0, True) assert LT(erfc(sqrt(a/t)/2), t, s) == (exp(-sqrt(a)*sqrt(s))/s, 0, True) # Bessel functions (laplace8.pdf) assert LT(besselj(0, a*t), t, s) == (1/sqrt(a**2 + s**2), 0, True) assert LT(besselj(1, a*t), t, s) ==\ (a/(sqrt(a**2 + s**2)*(s + sqrt(a**2 + s**2))), 0, True) assert LT(besselj(2, a*t), t, s) ==\ (a**2/(sqrt(a**2 + s**2)*(s + sqrt(a**2 + s**2))**2), 0, True) assert LT(t*besselj(0, a*t), t, s) ==\ (s/(a**2 + s**2)**(S(3)/2), 0, True) assert LT(t*besselj(1, a*t), t, s) ==\ (a/(a**2 + s**2)**(S(3)/2), 0, True) assert LT(t**2*besselj(2, a*t), t, s) ==\ (3*a**2/(a**2 + s**2)**(S(5)/2), 0, True) assert LT(besselj(0, 2*sqrt(a*t)), t, s) == (exp(-a/s)/s, 0, True) assert LT(t**(S(3)/2)*besselj(3, 2*sqrt(a*t)), t, s) ==\ (a**(S(3)/2)*exp(-a/s)/s**4, 0, True) assert LT(besselj(0, a*sqrt(t**2+b*t)), t, s) ==\ (exp(b*s - b*sqrt(a**2 + s**2))/sqrt(a**2 + s**2), 0, True) assert LT(besseli(0, a*t), t, s) == (1/sqrt(-a**2 + s**2), a, True) assert LT(besseli(1, a*t), t, s) ==\ (a/(sqrt(-a**2 + s**2)*(s + sqrt(-a**2 + s**2))), a, True) assert LT(besseli(2, a*t), t, s) ==\ (a**2/(sqrt(-a**2 + s**2)*(s + sqrt(-a**2 + s**2))**2), a, True) assert LT(t*besseli(0, a*t), t, s) == (s/(-a**2 + s**2)**(S(3)/2), a, True) assert LT(t*besseli(1, a*t), t, s) == (a/(-a**2 + s**2)**(S(3)/2), a, True) assert LT(t**2*besseli(2, a*t), t, s) ==\ (3*a**2/(-a**2 + s**2)**(S(5)/2), a, True) assert LT(t**(S(3)/2)*besseli(3, 2*sqrt(a*t)), t, s) ==\ (a**(S(3)/2)*exp(a/s)/s**4, 0, True) assert LT(bessely(0, a*t), t, s) ==\ (-2*asinh(s/a)/(pi*sqrt(a**2 + s**2)), 0, True) assert LT(besselk(0, a*t), t, s) ==\ (log(s + sqrt(-a**2 + s**2))/sqrt(-a**2 + s**2), a, True) assert LT(sin(a*t)**8, t, s) ==\ (40320*a**8/(s*(147456*a**8 + 52480*a**6*s**2 + 4368*a**4*s**4 +\ 120*a**2*s**6 + s**8)), 0, True) # Test general rules and unevaluated forms # These all also test whether issue #7219 is solved. assert LT(Heaviside(t-1)*cos(t-1), t, s) == (s*exp(-s)/(s**2 + 1), 0, True) assert LT(a*f(t), t, w) == a*LaplaceTransform(f(t), t, w) assert LT(a*Heaviside(t+1)*f(t+1), t, s) ==\ a*LaplaceTransform(f(t + 1)*Heaviside(t + 1), t, s) assert LT(a*Heaviside(t-1)*f(t-1), t, s) ==\ a*LaplaceTransform(f(t), t, s)*exp(-s) assert LT(b*f(t/a), t, s) == a*b*LaplaceTransform(f(t), t, a*s) assert LT(exp(-f(x)*t), t, s) == (1/(s + f(x)), -f(x), True) assert LT(exp(-a*t)*f(t), t, s) == LaplaceTransform(f(t), t, a + s) assert LT(exp(-a*t)*erfc(sqrt(b/t)/2), t, s) ==\ (exp(-sqrt(b)*sqrt(a + s))/(a + s), -a, True) assert LT(sinh(a*t)*f(t), t, s) ==\ LaplaceTransform(f(t), t, -a+s)/2 - LaplaceTransform(f(t), t, a+s)/2 assert LT(sinh(a*t)*t, t, s) ==\ (-1/(2*(a + s)**2) + 1/(2*(-a + s)**2), a, True) assert LT(cosh(a*t)*f(t), t, s) ==\ LaplaceTransform(f(t), t, -a+s)/2 + LaplaceTransform(f(t), t, a+s)/2 assert LT(cosh(a*t)*t, t, s) ==\ (1/(2*(a + s)**2) + 1/(2*(-a + s)**2), a, True) assert LT(sin(a*t)*f(t), t, s) ==\ I*(-LaplaceTransform(f(t), t, -I*a + s) +\ LaplaceTransform(f(t), t, I*a + s))/2 assert LT(sin(a*t)*t, t, s) ==\ (2*a*s/(a**4 + 2*a**2*s**2 + s**4), 0, True) assert LT(cos(a*t)*f(t), t, s) ==\ LaplaceTransform(f(t), t, -I*a + s)/2 +\ LaplaceTransform(f(t), t, I*a + s)/2 assert LT(cos(a*t)*t, t, s) ==\ ((-a**2 + s**2)/(a**4 + 2*a**2*s**2 + s**4), 0, True) # The following two lines test whether issues #5813 and #7176 are solved. assert LT(diff(f(t), (t, 1)), t, s) == s*LaplaceTransform(f(t), t, s)\ - f(0) assert LT(diff(f(t), (t, 3)), t, s) == s**3*LaplaceTransform(f(t), t, s)\ - s**2*f(0) - s*Subs(Derivative(f(t), t), t, 0)\ - Subs(Derivative(f(t), (t, 2)), t, 0) assert LT(a*f(b*t)+g(c*t), t, s) == a*LaplaceTransform(f(t), t, s/b)/b +\ LaplaceTransform(g(t), t, s/c)/c assert inverse_laplace_transform( f(w), w, t, plane=0) == InverseLaplaceTransform(f(w), w, t, 0) assert LT(f(t)*g(t), t, s) == LaplaceTransform(f(t)*g(t), t, s) # additional basic tests from wikipedia assert LT((t - a)**b*exp(-c*(t - a))*Heaviside(t - a), t, s) == \ ((s + c)**(-b - 1)*exp(-a*s)*gamma(b + 1), -c, True) assert LT((exp(2*t) - 1)*exp(-b - t)*Heaviside(t)/2, t, s, noconds=True) \ == exp(-b)/(s**2 - 1) # DiracDelta function: standard cases assert LT(DiracDelta(t), t, s) == (1, 0, True) assert LT(DiracDelta(a*t), t, s) == (1/a, 0, True) assert LT(DiracDelta(t/42), t, s) == (42, 0, True) assert LT(DiracDelta(t+42), t, s) == (0, 0, True) assert LT(DiracDelta(t)+DiracDelta(t-42), t, s) == \ (1 + exp(-42*s), 0, True) assert LT(DiracDelta(t)-a*exp(-a*t), t, s) == (s/(a + s), 0, True) assert LT(exp(-t)*(DiracDelta(t)+DiracDelta(t-42)), t, s) == \ (exp(-42*s - 42) + 1, -oo, True) # Collection of cases that cannot be fully evaluated and/or would catch # some common implementation errors assert LT(DiracDelta(t**2), t, s) == LaplaceTransform(DiracDelta(t**2), t, s) assert LT(DiracDelta(t**2 - 1), t, s) == (exp(-s)/2, -oo, True) assert LT(DiracDelta(t*(1 - t)), t, s) == \ LaplaceTransform(DiracDelta(-t**2 + t), t, s) assert LT((DiracDelta(t) + 1)*(DiracDelta(t - 1) + 1), t, s) == \ (LaplaceTransform(DiracDelta(t)*DiracDelta(t - 1), t, s) + \ 1 + exp(-s) + 1/s, 0, True) assert LT(DiracDelta(2*t-2*exp(a)), t, s) == (exp(-s*exp(a))/2, 0, True) assert LT(DiracDelta(-2*t+2*exp(a)), t, s) == (exp(-s*exp(a))/2, 0, True) # Heaviside tests assert LT(Heaviside(t), t, s) == (1/s, 0, True) assert LT(Heaviside(t - a), t, s) == (exp(-a*s)/s, 0, True) assert LT(Heaviside(t-1), t, s) == (exp(-s)/s, 0, True) assert LT(Heaviside(2*t-4), t, s) == (exp(-2*s)/s, 0, True) assert LT(Heaviside(-2*t+4), t, s) == ((1 - exp(-2*s))/s, 0, True) assert LT(Heaviside(2*t+4), t, s) == (1/s, 0, True) assert LT(Heaviside(-2*t+4), t, s) == ((1 - exp(-2*s))/s, 0, True) # Fresnel functions assert laplace_transform(fresnels(t), t, s) == \ ((-sin(s**2/(2*pi))*fresnels(s/pi) + sin(s**2/(2*pi))/2 - cos(s**2/(2*pi))*fresnelc(s/pi) + cos(s**2/(2*pi))/2)/s, 0, True) assert laplace_transform(fresnelc(t), t, s) == ( ((2*sin(s**2/(2*pi))*fresnelc(s/pi) - 2*cos(s**2/(2*pi))*fresnels(s/pi) + sqrt(2)*cos(s**2/(2*pi) + pi/4))/(2*s), 0, True)) # Matrix tests Mt = Matrix([[exp(t), t*exp(-t)], [t*exp(-t), exp(t)]]) Ms = Matrix([[ 1/(s - 1), (s + 1)**(-2)], [(s + 1)**(-2), 1/(s - 1)]]) # The default behaviour for Laplace tranform of a Matrix returns a Matrix # of Tuples and is deprecated: with warns_deprecated_sympy(): Ms_conds = Matrix([[(1/(s - 1), 1, True), ((s + 1)**(-2), -1, True)], [((s + 1)**(-2), -1, True), (1/(s - 1), 1, True)]]) with warns_deprecated_sympy(): assert LT(Mt, t, s) == Ms_conds # The new behavior is to return a tuple of a Matrix and the convergence # conditions for the matrix as a whole: assert LT(Mt, t, s, legacy_matrix=False) == (Ms, 1, True) # With noconds=True the transformed matrix is returned without conditions # either way: assert LT(Mt, t, s, noconds=True) == Ms assert LT(Mt, t, s, legacy_matrix=False, noconds=True) == Ms
from sympy.integrals.transforms import inverse_laplace_transform from sympy.abc import symbols t, s = symbols('t,s', positive=True) ans1 = inverse_laplace_transform((1 / (s + 3)**3), s, t) print("18MEC24006-DENNY JOHNSON P") print(ans1) ans2 = inverse_laplace_transform((3 * s**2 + 10 * s - 6) / s**4, s, t) print(ans2) ans3 = inverse_laplace_transform(s / (s - 3)**5, s, t) print(ans3) ans4 = inverse_laplace_transform((2 * s - 11) / (s**2 + 4 * s + 8), s, t) print(ans4)
from sympy import * from sympy.integrals.transforms import laplace_transform,inverse_laplace_transform from sympy.simplify.fu import L s,L=symbols('s,L') t=symbols('t',positive=True) y0=2 y10=1 Ly2=s**2*L-s*y0-y10 Ly1=s*L-y0 Ly=L algeq=Eq(Ly2+Ly1-2*Ly,laplace_transform(4,t,s,noconds=True)) print("18MEC24006-DENNY JOHNSON P") print(algeq) algsoln=solve(algeq,L)[0] print(algsoln) soln=inverse_laplace_transform(algsoln,s,t,noconds=True) print("Solution:y(t)=",soln)
def test_laplace_transform(): from sympy import fresnels, fresnelc LT = laplace_transform a, b, c, = symbols("a b c", positive=True) t = symbols("t") w = Symbol("w") f = Function("f") # Test unevaluated form assert laplace_transform(f(t), t, w) == LaplaceTransform(f(t), t, w) assert inverse_laplace_transform(f(w), w, t, plane=0) == InverseLaplaceTransform(f(w), w, t, 0) # test a bug spos = symbols("s", positive=True) assert LT(exp(t), t, spos)[:2] == (1 / (spos - 1), True) # basic tests from wikipedia assert LT((t - a) ** b * exp(-c * (t - a)) * Heaviside(t - a), t, s) == ( (s + c) ** (-b - 1) * exp(-a * s) * gamma(b + 1), -c, True, ) assert LT(t ** a, t, s) == (s ** (-a - 1) * gamma(a + 1), 0, True) assert LT(Heaviside(t), t, s) == (1 / s, 0, True) assert LT(Heaviside(t - a), t, s) == (exp(-a * s) / s, 0, True) assert LT(1 - exp(-a * t), t, s) == (a / (s * (a + s)), 0, True) assert LT((exp(2 * t) - 1) * exp(-b - t) * Heaviside(t) / 2, t, s, noconds=True) == exp(-b) / (s ** 2 - 1) assert LT(exp(t), t, s)[:2] == (1 / (s - 1), 1) assert LT(exp(2 * t), t, s)[:2] == (1 / (s - 2), 2) assert LT(exp(a * t), t, s)[:2] == (1 / (s - a), a) assert LT(log(t / a), t, s) == ((log(a * s) + EulerGamma) / s / -1, 0, True) assert LT(erf(t), t, s) == ((erfc(s / 2)) * exp(s ** 2 / 4) / s, 0, True) assert LT(sin(a * t), t, s) == (a / (a ** 2 + s ** 2), 0, True) assert LT(cos(a * t), t, s) == (s / (a ** 2 + s ** 2), 0, True) # TODO would be nice to have these come out better assert LT(exp(-a * t) * sin(b * t), t, s) == (b / (b ** 2 + (a + s) ** 2), -a, True) assert LT(exp(-a * t) * cos(b * t), t, s) == ((a + s) / (b ** 2 + (a + s) ** 2), -a, True) assert LT(besselj(0, t), t, s) == (1 / sqrt(1 + s ** 2), 0, True) assert LT(besselj(1, t), t, s) == (1 - 1 / sqrt(1 + 1 / s ** 2), 0, True) # TODO general order works, but is a *mess* # TODO besseli also works, but is an even greater mess # test a bug in conditions processing # TODO the auxiliary condition should be recognised/simplified assert LT(exp(t) * cos(t), t, s)[:-1] in [ ((s - 1) / (s ** 2 - 2 * s + 2), -oo), ((s - 1) / ((s - 1) ** 2 + 1), -oo), ] # Fresnel functions assert laplace_transform(fresnels(t), t, s) == ( ( -sin(s ** 2 / (2 * pi)) * fresnels(s / pi) + sin(s ** 2 / (2 * pi)) / 2 - cos(s ** 2 / (2 * pi)) * fresnelc(s / pi) + cos(s ** 2 / (2 * pi)) / 2 ) / s, 0, True, ) assert laplace_transform(fresnelc(t), t, s) == ( ( sin(s ** 2 / (2 * pi)) * fresnelc(s / pi) / s - cos(s ** 2 / (2 * pi)) * fresnels(s / pi) / s + sqrt(2) * cos(s ** 2 / (2 * pi) + pi / 4) / (2 * s), 0, True, ) ) assert LT(Matrix([[exp(t), t * exp(-t)], [t * exp(-t), exp(t)]]), t, s) == Matrix( [[(1 / (s - 1), 1, True), ((s + 1) ** (-2), 0, True)], [((s + 1) ** (-2), 0, True), (1 / (s - 1), 1, True)]] )
x_1 = A_result * x_2 print(x_1) #u_1 = inverse_laplace_transform(x_1[0], s, t) x = Matrix([U, -I]) ODE = A_result * x - x ## Beispiel aus der Pub 0D/3D coupling A_result_2 = A_R(R_p) * A_C(C) * A_R(R_d) #x_val = Matrix([0, -I]) x_val = Matrix([0, -(1 / (2 * s**3 + 2 * s))]) res = A_result_2 * x_val P_ex = inverse_laplace_transform(res[0], s, t) # #A_ex = A_L(L)*A_R(R)*A_R(R)*A_C(C)*A_L(L) # #A_ex_2 = A_R(R)*A_C(C)*A_L(L)*A_L(L)*A_R(R) # #A_ex_3 = A_C(C)*A_L(L)*A_R(R) # #A_ex_4 = A_L(L)*A_R(R)*A_C(C) # #eig = A_ex.eigenvals() # #factor_list(expand(A_ex[1])) #testing = expand(A_ex[1]) #a = Poly(testing, s)
def test_laplace_transform(): from sympy import fresnels, fresnelc, DiracDelta LT = laplace_transform a, b, c, = symbols('a b c', positive=True) t = symbols('t') w = Symbol("w") f = Function("f") # Test unevaluated form assert laplace_transform(f(t), t, w) == LaplaceTransform(f(t), t, w) assert inverse_laplace_transform(f(w), w, t, plane=0) == InverseLaplaceTransform( f(w), w, t, 0) # test a bug spos = symbols('s', positive=True) assert LT(exp(t), t, spos)[:2] == (1 / (spos - 1), 1) # basic tests from wikipedia assert LT((t - a)**b*exp(-c*(t - a))*Heaviside(t - a), t, s) == \ ((s + c)**(-b - 1)*exp(-a*s)*gamma(b + 1), -c, True) assert LT(t**a, t, s) == (s**(-a - 1) * gamma(a + 1), 0, True) assert LT(Heaviside(t), t, s) == (1 / s, 0, True) assert LT(Heaviside(t - a), t, s) == (exp(-a * s) / s, 0, True) assert LT(1 - exp(-a * t), t, s) == (a / (s * (a + s)), 0, True) assert LT((exp(2*t) - 1)*exp(-b - t)*Heaviside(t)/2, t, s, noconds=True) \ == exp(-b)/(s**2 - 1) assert LT(exp(t), t, s)[:2] == (1 / (s - 1), 1) assert LT(exp(2 * t), t, s)[:2] == (1 / (s - 2), 2) assert LT(exp(a * t), t, s)[:2] == (1 / (s - a), a) assert LT(log(t / a), t, s) == ((log(a * s) + EulerGamma) / s / -1, 0, True) assert LT(erf(t), t, s) == (erfc(s / 2) * exp(s**2 / 4) / s, 0, True) assert LT(sin(a * t), t, s) == (a / (a**2 + s**2), 0, True) assert LT(cos(a * t), t, s) == (s / (a**2 + s**2), 0, True) # TODO would be nice to have these come out better assert LT(exp(-a * t) * sin(b * t), t, s) == (b / (b**2 + (a + s)**2), -a, True) assert LT(exp(-a*t)*cos(b*t), t, s) == \ ((a + s)/(b**2 + (a + s)**2), -a, True) assert LT(besselj(0, t), t, s) == (1 / sqrt(1 + s**2), 0, True) assert LT(besselj(1, t), t, s) == (1 - 1 / sqrt(1 + 1 / s**2), 0, True) # TODO general order works, but is a *mess* # TODO besseli also works, but is an even greater mess # test a bug in conditions processing # TODO the auxiliary condition should be recognised/simplified assert LT(exp(t) * cos(t), t, s)[:-1] in [ ((s - 1) / (s**2 - 2 * s + 2), -oo), ((s - 1) / ((s - 1)**2 + 1), -oo), ] # DiracDelta function: standard cases assert LT(DiracDelta(t), t, s) == (1, -oo, True) assert LT(DiracDelta(a * t), t, s) == (1 / a, -oo, True) assert LT(DiracDelta(t / 42), t, s) == (42, -oo, True) assert LT(DiracDelta(t + 42), t, s) == (0, -oo, True) assert LT(DiracDelta(t)+DiracDelta(t-42), t, s) == \ (1 + exp(-42*s), -oo, True) assert LT(DiracDelta(t) - a * exp(-a * t), t, s) == (-a / (a + s) + 1, 0, True) assert LT(exp(-t)*(DiracDelta(t)+DiracDelta(t-42)), t, s) == \ (exp(-42*s - 42) + 1, -oo, True) # Collection of cases that cannot be fully evaluated and/or would catch # some common implementation errors assert LT(DiracDelta(t**2), t, s) == LaplaceTransform(DiracDelta(t**2), t, s) assert LT(DiracDelta(t**2 - 1), t, s) == (exp(-s) / 2, -oo, True) assert LT(DiracDelta(t*(1 - t)), t, s) == \ LaplaceTransform(DiracDelta(-t**2 + t), t, s) assert LT((DiracDelta(t) + 1)*(DiracDelta(t - 1) + 1), t, s) == \ (LaplaceTransform(DiracDelta(t)*DiracDelta(t - 1), t, s) + \ 1 + exp(-s) + 1/s, 0, True) assert LT(DiracDelta(2*t - 2*exp(a)), t, s) == \ (exp(-s*exp(a))/2, -oo, True) # Fresnel functions assert laplace_transform(fresnels(t), t, s) == \ ((-sin(s**2/(2*pi))*fresnels(s/pi) + sin(s**2/(2*pi))/2 - cos(s**2/(2*pi))*fresnelc(s/pi) + cos(s**2/(2*pi))/2)/s, 0, True) assert laplace_transform( fresnelc(t), t, s) == (((2 * sin(s**2 / (2 * pi)) * fresnelc(s / pi) - 2 * cos(s**2 / (2 * pi)) * fresnels(s / pi) + sqrt(2) * cos(s**2 / (2 * pi) + pi / 4)) / (2 * s), 0, True)) # What is this testing: Ne(1 / s, 1) & (0 < cos(Abs(periodic_argument(s, oo))) * Abs(s) - 1) Mt = Matrix([[exp(t), t * exp(-t)], [t * exp(-t), exp(t)]]) Ms = Matrix([[1 / (s - 1), (s + 1)**(-2)], [(s + 1)**(-2), 1 / (s - 1)]]) # The default behaviour for Laplace tranform of a Matrix returns a Matrix # of Tuples and is deprecated: with warns_deprecated_sympy(): Ms_conds = Matrix([[(1 / (s - 1), 1, s > 1), ((s + 1)**(-2), 0, True)], [((s + 1)**(-2), 0, True), (1 / (s - 1), 1, s > 1)]]) with warns_deprecated_sympy(): assert LT(Mt, t, s) == Ms_conds # The new behavior is to return a tuple of a Matrix and the convergence # conditions for the matrix as a whole: assert LT(Mt, t, s, legacy_matrix=False) == (Ms, 1, s > 1) # With noconds=True the transformed matrix is returned without conditions # either way: assert LT(Mt, t, s, noconds=True) == Ms assert LT(Mt, t, s, legacy_matrix=False, noconds=True) == Ms