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#
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# wpylib.math.fitting.funcs_physics module
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# Created: 20150521
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# Wirawan Purwanto
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#
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# Imported 20150521 from Cr2_analysis_cbs.py
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# (dated 20141017, CVS rev 1.143).
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#
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"""
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wpylib.math.fitting.funcs_physics module
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A library of simple f(x) functions for physics-related common functional fitting
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For use with OO-style x-y curve fitting interface.
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"""
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import numpy
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from wpylib.math.fitting import fit_func_base
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class FermiDirac_fit_func(fit_func_base):
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"""Fermi-Dirac function object.
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For use with fit_func function.
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Functional form:
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C[0] * (exp((x - C[1]) / C[2]) + 1)^-1
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Coefficients:
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* C[0] = amplitude
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* C[1] = transition "temperature"
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* C[2] = "smearing temperature"
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"""
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dim = 1 # a function with 1-D domain
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param_names = ('A', 'F', 'T')
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# FIXME: Not good yet!!!
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F_guess = 1.9
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T_guess = 0.05
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def __call__(self, C, x):
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from numpy import exp
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A, F, T = self.get_params(C, *(self.param_names))
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y = A * (exp((x[0] - F) / T) + 1)**(-1)
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self.func_call_hook(C, x, y)
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return y
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def Guess_xy(self, x, y):
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imin = numpy.argmin(y)
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self.guess_params = (y[imin], self.F_guess, self.T_guess)
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return self.guess_params
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