* Fitting seemed to work, but still not perfectly. Do not use in production

yet.
master
wirawan 15 years ago
parent c87ba9dbfa
commit adbe499db8
  1. 66
      math/fitting.py

@ -1,4 +1,4 @@
# $Id: fitting.py,v 1.1 2010-01-22 18:44:59 wirawan Exp $
# $Id: fitting.py,v 1.2 2010-05-28 18:43:39 wirawan Exp $
#
# wpylib.math.fitting module
# Created: 20100120
@ -118,18 +118,27 @@ class Poly_order4(Poly_base):
def fit_func(Funct, Data=None, Guess=None, x=None, y=None):
'''
def fit_func(Funct, Data=None, Guess=None, x=None, y=None,
debug=10,
method='leastsq', opts={}):
"""
Performs a function fitting.
The domain of the function is a D-dimensional vector, and the function
yields a scalar.
Funct is a python function (or any callable object) with argument list of
(C, x), where:
* C is the cofficients (parameters) to be adjusted by the fitting process
* C is the cofficients (parameters) being adjusted by the fitting process
(it is a sequence or a 1-D array)
* x is a 2-D array (or sequence of like nature). The "row" size is the dimensionality
of the domain, while the "column" is the number of data points, whose count must be
equal to the size of y data below.
* x is a 2-D array (or sequence of like nature), say,
of size "N rows times M columns".
N is the dimensionality of the domain, while
M is the number of data points, whose count must be equal to the
size of y data below.
For a 2-D fitting, for example, x should be a column array.
Inspect Poly_base, Poly_order2, and other similar function classes in this module
to see the example of the Funct function.
Inspect Poly_base, Poly_order2, and other similar function classes in this
module to see the example of the Funct function.
The measurement (input) datasets, against which the function is to be fitted,
can be specified in one of two ways:
@ -139,11 +148,10 @@ def fit_func(Funct, Data=None, Guess=None, x=None, y=None):
Or,
* via Data argument (which is a multi-column dataset
'''
"""
global last_fit_rslt, last_chi_sqr
from scipy.optimize import leastsq
from scipy.optimize import leastsq, anneal
# We want to minimize this error:
fun_err = lambda CC, xx, yy: abs(Funct(CC,xx) - yy)
if Data != None: # an alternative way to specifying x and y
y = Data[0]
x = Data[1:] # possibly multidimensional!
@ -152,12 +160,36 @@ def fit_func(Funct, Data=None, Guess=None, x=None, y=None):
Guess = Funct.Guess(y)
elif Guess == None: # VERY OLD, DO NOT USE ANYMORE!
Guess = [ y.mean() ] + [0.0, 0.0] * len(x)
rslt = leastsq(fun_err,
x0=Guess, # initial coefficient guess
args=(x,y), # data onto which the function is fitted
full_output=1)
fun_err = lambda CC, xx, yy: abs(Funct(CC,xx) - yy)
fun_err2 = lambda CC, xx, yy: numpy.sum(abs(Funct(CC,xx) - yy)**2)
if debug >= 5:
print "Guess params:"
print Guess
if method == 'leastsq':
rslt = leastsq(fun_err,
x0=Guess, # initial coefficient guess
args=(x,y), # data onto which the function is fitted
full_output=1,
**opts
)
elif method == 'anneal':
rslt = anneal(fun_err2,
x0=Guess, # initial coefficient guess
args=(x,y), # data onto which the function is fitted
full_output=1,
**opts
)
else:
raise ValueError, "Unsupported minimization method: %s" % method
last_fit_rslt = rslt
last_chi_sqr = sum( fun_err(rslt[0], x, y)**2 )
last_chi_sqr = fun_err2(rslt[0], x, y)
if (debug >= 10):
#print "Fit-message: ", rslt[]
print "Fit-result:"
print "\n".join([ "%2d %s" % (ii, rslt[ii]) for ii in xrange(len(rslt)) ])
print "params = ", rslt[0]
print "chi square = ", last_chi_sqr / len(y)
return rslt[0]

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