Hello, I'd like to know if there's a way in MATLAB to solve a symbolic system of equations with symbolic coefficients ? Thanks for your help.

Yes, the symbolic math toolbox will do this. Type mupad at the matlab command prompt, then dig into the help files and documentation to find your feet. Overview and examples here:

SYMBOLIC system of equations

hugg 2012-9-12

Thanks Gruff for your prompt answer.

I am currently looking into Mupad.

I need a function equivalent to linsolve to solve a fully symbolic linear system of equations (the unknowns as well as the coefficients are Symolic). I am not sure this is handled by Matlab, but I may be mistaken (I hope).

Thanks for your help.

Walter Roberson 2012-9-12

solve() should be able to do it.

hugg 2012-9-12

编辑：hugg 2012-9-12

Thanks Walter. However solve does not deal with matrix forms (please correct me if I am mistaken).

I have a matrix expression :

A.X = B

All matrices are symbolic. Is there a function in matlab to solve the above equation for X (A and B are parameters).

Thanks.

Walter Roberson 2012-9-12

I think I read that as of R2012a, you can use the \ operator on symbolic arrays.

Otherwise, you can do the symbolic matrix multiply and solve() that.

hugg 2012-9-12

I have R2009b version.

I'm not sure I get what you said regarding the \ ? (do mean to devide vector B by matrix A ?).

I think that if there is no function dealing with matrix symbolic linear equation I will rewrite it as a system of polynomial expressions.

Thanks again !

Walter Roberson 2012-9-12

Notice that in the (current) linsolve documentation http://www.mathworks.com/help/symbolic/linsolve.html that the example involves symbolic A and B, which is what you are looking for.

hugg 2012-9-12

Thank you Walter.

I looked into it. It seems you are right.

hugg 2012-9-12

I tried the example http://www.mathworks.com/help/symbolic/linsolve.html on my Matlab and it generates this error message : "??? Undefined function or method 'linsolve' for input arguments of type 'sym'.".

I guess this is due to the old version of Matlab I am running (R2009b).

It looks like I got the answer to my question.

Thank you guys for your answers.

Walter Roberson 2012-9-12

You might be able to find something in MuPADs linalg library. http://www.mathworks.com/help/symbolic/mupad_ug/using-the-mupad-libraries.html and http://www.mathworks.com/help/symbolic/mupad_ug/linear-algebra-library.html

Search your documentation for "standard library", as you will get a very different document (that has been removed in R2012b). http://www.mathworks.com/help/releases/R2009b/toolbox/mupad/linalg/ and http://www.mathworks.com/help/releases/R2009b/toolbox/mupad/stdlib/

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