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Asked by R on 21 Aug 2014

Hi, I am new to this forum and have little experience with MATLAB. I would appreciate your help with the following question.

Is there a function or a toolbox in MATLAB that allows to estimate non-linear regression model parameters jointly?

I have two non-linear regression models to estimate jointly.

Thanks, R

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Answer by Star Strider on 21 Aug 2014

I do not understand what you mean by ‘jointly’, but there are three possible functions you can use: `nlinfit` (Statistics Toolbox), `lsqcurvefit` (Optimization Toolbox) or (with an extra line of code) the core `MATLAB` function `fminsearch`.

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Star Strider on 22 Aug 2014 at 14:14

I still have no idea what you want to do.

Again:

- What are your independent
`(‘x’)`and dependent`(‘y’)`variables*with respect to the equations you posted*? - Are you fitting one dependent variable or two?

Star Strider on 22 Aug 2014 at 15:52

I can help you with the nonlinear regression functions that I mentioned in my original Answer, but you need to code your objective functions in terms of the parameters and independent variables, as described in the documentation for ** nlinfit** or

Star Strider on 22 Aug 2014 at 16:43

The `lsqcurvefit` function can fit matrix dependent variables, but since it is impossible for me to figure out what your independent and dependent variables are, I can’t help you to code them.

It looks as though they are nonlinear equations log-transformed to make them linear. (This is definitely not a recommended practice.)

Post the *original* equations (not the log-transformed versions), *specify your independent and dependent variables*, make a sincere attempt at coding them, and I can help you fit them with `lsqcurvefit`.

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