[SciPy-user] Another leastsq Jacobian bug

Christian K ckkart@hoc....
Mon Jun 25 22:33:35 CDT 2007


Lin Shao wrote:
>>> ## Now define my Jacobian
>>> def Jacobian(params,xx,yy,mode='col'):
>>>     J = N.empty((len(params),xx.size))
>>>     J[0] = (xx-params[1])**2
>>>     J[1] = -2*params[0]*(xx-params[1])
>> shouldn't that be -2*params[0]*(xx-params[1])*params[1]  ?
> 
> I think I was right. Think about what's the derivative of -x^2 -- it's -2x

you forgot about the chain rule .

Christian



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