[SciPy-User] Problem using curve_fit function

Gökhan Sever gokhansever@gmail....
Wed Apr 21 00:21:34 CDT 2010


Hello,

I want to fit a curve to my simple data using the scipy.optimize.curve_fit
function. Here how I define my arrays and fit function:

    tfit = np.array([463.8, 0.5])
    weights = np.ones(16, dtype='float64')
    popt, pcov = curve_fit(my_func, array([16 elements x]), array([16
elements y]), p0=tfit, sigma=weights)

   def my_func(x, a, b):
       return a*x**b

I am following the documentation and example from
http://docs.scipy.org/doc/scipy/reference/generated/scipy.optimize.curve_fit.html

When I run the script, this part of the code produces a RunTimeError as
indicated below:

  File "/usr/lib/python2.6/site-packages/scipy/optimize/minpack.py", line
430, in curve_fit
    raise RuntimeError(msg)
RuntimeError: Optimal parameters not found: The cosine of the angle between
func(x) and any column of the
  Jacobian is at most 0.000000 in absolute value

Do you have any ideas how to fix this issue and estimate optimum parameters
out of my data?

Thank you.

-- 
Gökhan
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