def estimateSigma(self, gamma_sigma, param, K, F, T):
a = self._a
#param=np.exp(param) #transform to restrict a to be postive
effective_K = 1 - np.exp(-a * T) * (1 - K / F)
f0 = F + gamma_sigma[0]
k0 = effective_K * F + gamma_sigma[0]
d1 = (np.log(f0 / k0) +
(r + 0.5 * gamma_sigma[1]**2) * T) / (gamma_sigma[1] *
np.sqrt(T))
d2 = d1 - gamma_sigma[1] * np.sqrt(T)
#call_price = np.exp(a*T)/F *(f0*norm.cdf(d1)-k0*norm.cdf(d2))
f1 = -2 * a * (effective_K - 1) * ndtr(d2) * np.exp(a * T)
f2 = 4 * a**2 * (effective_K - 1)**2 * ndtr(d2)**2 * np.exp(2 * a * T)
f3 = f0**2 * norm._pdf(d1)**2 * np.exp(a * T) * effective_K**2
f4 = f0 * norm._pdf(d1) / (F * np.sqrt(T))
estimate_sigma = (f1 +
np.sqrt(f2 +
(f3 *
(param[0] * effective_K + param[1])**2) /
(k0**2 * np.sqrt(T)))) / f4
return estimate_sigma
def tn_pdf(x, loc, scale, lower=0, upper=1):
if upper == np.inf:
Z = 1 - norm._cdf(lower-loc/scale)
else:
Z = norm._cdf((upper-loc)/scale) - norm._cdf((lower-loc)/scale)
pdf_psi = norm._pdf((x - loc) / scale)
return pdf_psi / (scale * Z)
def vega(self):
vegaCall = self.S * norm._pdf(self.d1) * np.sqrt(self.T)
vegaPut = vegaCall
return namedtuple('Vega', ['call', 'put'])(**{
"call": vegaCall,
"put": vegaPut
})
def gamma(self):
gammaCall = norm._pdf(self.d1) / float(
self.S * self.sigma * np.sqrt(self.T))
gammaPut = gammaCall
return namedtuple('Gamma', ['call', 'put'])(**{
"call": gammaCall,
"put": gammaPut
})
def theoreticalDistribution(self, strikes):
probability = []
for strike in strikes:
probability.append(norm._pdf(self.computeValues(strike=strike).d2))
return namedtuple('Distruibution',
['strike', 'probability'])(**{
"strike": strikes,
"probability": probability
})
def theta(self):
thetaCall = -self.K * self.r * np.exp(-self.r * self.T) * ndtr(
self.d2) - (self.sigma * self.S * norm._pdf(self.d1) /
(2 * np.sqrt(self.T)))
thetaPut = self.K * self.r * np.exp(-self.r * self.T) + thetaCall
return namedtuple('Theta', ['call', 'put'])(**{
"call": thetaCall,
"put": thetaPut
})
def implied_vol(mkt_price, F, K, T_maturity, *args):
Max_iteration = 500
PRECISION = 1.0e-5
sigma = 0.4
for i in range(0, Max_iteration):
d1 = (np.log(F / K) + ( 0.5 * sigma ** 2) * T_maturity) / (sigma * np.sqrt(T_maturity))
d2 = d1 - sigma * np.sqrt(T_maturity)
bls_price = F * ndtr(d1) - K * ndtr(d2)
vega = F * norm._pdf(d1) * np.sqrt(T_maturity)
diff = mkt_price - bls_price
if (abs(diff) < PRECISION):
return sigma
sigma = sigma + diff/vega # f(x) / f'(x)
return sigma
def compute_delta(current_price, strike, interest_rate, days_to_expiry,
option_price, is_call):
# epsilon is how far off the guess is
epsilon = 1
# initial guess is 0.5
volatility = 0.50
t = days_to_expiry / 365.0
# This calculator assumes the interest rate is a percent
interest_rate = interest_rate / 100.0
for _ in range(MAX_ITERATIONS):
# Log the value previously calculated to computer percent change
# between iterations
orig_volatility = volatility
# Calculate the value of the call price
d1, d2 = d(volatility, current_price, strike, interest_rate, t)
if is_call:
value = call_price(volatility, current_price, strike,
interest_rate, t, d1, d2) - option_price
else:
value = put_price(volatility, current_price, strike, interest_rate,
t, d1, d2) - option_price
# Calculate vega, the derivative of the price with respect to
# volatility
vega = current_price * norm._pdf(d1) * sqrt(t)
# Update for value of the volatility
volatility += -value / vega
# Check the percent change between current and last iteration
epsilon = abs((volatility - orig_volatility) / orig_volatility)
if epsilon < TOLERANCE:
break
# http://janroman.dhis.org/stud/I2014/BS2/BS_Daniel.pdf, compute put delta
return -ndtr(-d1)
def mytruncpdf_01bounds(x, loc, scale):
Z = norm._cdf((1-loc)/scale) - norm._cdf(-loc/scale)
pdf_psi = norm._pdf((x - loc) / scale)
return pdf_psi / (scale * Z)
def tn_pdf_01(x, loc, scale):
Z = norm._cdf((1-loc)/scale) - norm._cdf(-loc/scale)
pdf_psi = norm._pdf((x - loc) / scale)
return pdf_psi / (scale * Z)
