The quick and dirty way is to do a variable substitution with the square of your parameter and fit, e.g. r + (a**2)*np.power(x, -b**2) You can take the sqrt of the parameters later. ________________________________ From: servant mathieu <servant.mathieu@gmail.com> To: scipy-user@scipy.org Sent: Thursday, 17 May 2012 4:20 AM Subject: [SciPy-User] is it possible to constrain the scipy.optimize.curve_fit function? Dear scipy users, I'm trying to fit to data a power law of the form : def func (x, a,b, r): return r + a*np.power(x,-b) I would like to constrain the curve_fit routine to only allow positive parameter values. How is it possible to do so? Kind regards, Mathieu _______________________________________________ SciPy-User mailing list SciPy-User@scipy.org http://mail.scipy.org/mailman/listinfo/scipy-user