How to put limit on coefficient produced by polyfit in MATLAB?

Hello,

So what I am trying to do is plot some experimental data along with a second order polynomial fit (Ax^2 + Bx + C), the coefficients of which are determined using polyfit. The problem I am having is that I do not want the first term, in this case A to be negative. Is there any way I can put constraints on this A term so that it does not go below zero?

Any help would be appreciated.

[ali asakereh]

Hi Anna,

did you find the answer?

Answer 1

[Wayne King]

There are routines on the file exchange like this one:

http://www.mathworks.com/matlabcentral/fileexchange/38926-fit-polynomial-to-data-with-constraints

If you have the Optimization Toolbox, see

http://www.mathworks.com/help/optim/ug/least-squares-model-fitting-algorithms.html