def to_raw(self, val):
# only handle scalar val not arrays
func = lambda x: self.from_raw(x) - val
a, b = self._to_raw
# extend limits to make sure the limits are invertable
diff = b - a
a -= diff / 1e6
b += diff / 1e6
x = brentq_rootsolver(func, a, b)
return x
def to_raw(self, val):
# only handle scalar val not arrays
func = lambda x: self.from_raw(x)-val
a,b = self._to_raw
# extend limits to make sure the limits are invertable
diff = b-a
a -= diff/1e6
b += diff/1e6
x = brentq_rootsolver(func, a, b)
return x
def fraction_to_filter(frac=0.99, n_filter=1):
"""
Calculates the number of time constants to wait to achieve the requested
fractional change (frac) from a step function.
n_filter is the number of filters (all using the same time_constants non-interacting
(buffered in between each))
See also the inverse function filter_to_fraction
"""
if frac <= 0. or frac >= 1:
raise ValueError('frac is out of range need 0 < frac < 1')
if n_filter != int(n_filter):
old = n_filter
n_filter = int(n_filter)
print 'n_filter was not an integer (%r). Converted it to %i'%(old, n_filter)
if n_filter <= 0 or n_filter > 100:
raise ValueError('n_filter to be positive and non-zero (and not greater than 100)')
func = lambda x: filter_to_fraction(x, n_filter)-frac
n_time = brentq_rootsolver(func, 0, 1000)
return n_time
