[SciPy-User] leastsq error

stephen lukacs sjlukacs@gmail....
Sun Oct 28 20:02:09 CDT 2012


hello one and all,

i am having a terrible time with optimize.leastsq, even fitting a line, so 
please help.  here is my python code and error

>>> import numpy
>>> from scipy import optimize
>>> def expr_conductance(x, a, b, c):
...     return a*0 + b*x + c
... 
>>> def residual_conductance(p,x,y):
...     a, b, c = p
...     return y - expr_conductance(x, a, b, c)
... 
>>> x = [0.99771057137610752, 0.49976145827781415, 0.24821831884394957, 
0.12480215949109599, 0.06315070141095365, 0.03065779901355976, 
0.015669312142317458, 0.0078799613766362755, 0.0039027338918740067]
>>> len(x)
9
>>> y = [2.9954211427522148, 1.9995229165556283, 1.496436637687899, 
1.2496043189821919, 1.1263014028219074, 1.0613155980271196, 
1.031338624284635, 1.0157599227532725, 1.007805467783748]
>>> len(y)
9
>>> [a, b, c], conv = optimize.leastsq(residual_conductance, [0,10000.,5.], 
args = (x,y))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.6/site-packages/scipy/optimize/minpack.py", line 
276, in leastsq
    m = _check_func('leastsq', 'func', func, x0, args, n)[0]
  File "/usr/lib/python2.6/site-packages/scipy/optimize/minpack.py", line 
13, in _check_func
    res = atleast_1d(thefunc(*((x0[:numinputs],) + args)))
  File "<stdin>", line 3, in residual_conductance
ValueError: operands could not be broadcast together with shapes (9) 
(90000) 
>>> 

 i have tried many permutations and looked all over for syntax, but i can 
not find why this error is there or how to deal with it.  i have scipy 
0.10.1 and numpy 1.6.1 under python 2.6.6 on a centos 6.3 system. 
 ultimately i want to put make the fit function 
a*numpy.power(x,(3/2))+b*x+c, which is a bit nonlinear but at this point i 
can't even get a line to fit.

thank you in advance and have a great day.  lucas
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