/sci/ - Science & Math

Alright so i've got this set of points that i'm trying to fit into a gamma distribution with matlab so i can estimate theta. The trick is that I want to use custom gamma since I know the k parameter (yes for the set in the picture , k= 1 so i can fit it into an exponential quite straightforward, but I've got other distributions with other integer k parameters to fit afterwards).

First i tried with 'mle' function and with a custom pdf but I've had 'not enough input parameter' or 'NaN' kind of error, i suppose it's because my data isn't normalized.

Then I tried to use nlinfit but it says :
"Warning: Some columns of the Jacobian are effectively zero at the solution, indicating that the model is insensitive to some of its
parameters. That may be because those parameters are not present in the model, or otherwise do not affect the predicted values. It may
also be due to numerical underflow in the model function, which can sometimes be avoided by choosing better initial parameter values, or
by rescaling or recentering. Parameter estimates may be unreliable. "
and the estimate of theta is my starting value.

Can someone detail me a method for finding theta in matlab when sample points of the distribution and k are known please ?