Help with anonymous function, fsolve, and str2func

[Alicia]

I'm trying to write a code that uses fsolve to solve for missing variables in a set of non-linear equations. The problem is that it will be different variables that are missing for each run. So I'm using a loop to determine which variable is missing, and then putting that into a string. Then using the str2func function to turn the function with the equations (@isp) into an anonymous function that is only a function of the missing input (th).

This is the code:
f = str2func('@(th)isp(n,m,th)');
th = fsolve(f,0);

This is the error:
??? Undefined function or variable 'n'.
Error in ==> @(th)isp(n,m,th)
Error in ==> fsolve at 253
fuser = feval(funfcn{3},x,varargin{:});

I hope I explained that well enough. Please help!

Thanks!

[Matt J]

"Alicia " <ast...@asdl.gatech.edu> wrote in message <jshr8b$lbl$1...@newscl01ah.mathworks.com>...

>
> This is the error:
> ??? Undefined function or variable 'n'.
> Error in ==> @(th)isp(n,m,th)
> Error in ==> fsolve at 253
> fuser = feval(funfcn{3},x,varargin{:});
>
> I hope I explained that well enough. Please help!

================

The variable 'n' did not exist at the time you defined the anonymous function. Here's an example of the same error in isolation from other code,

>> clear all; f=@(a) sin(a+b); f(1)
Undefined function or variable 'b'.

Error in @(a)sin(a+b)

[Matt J]

"Alicia " <ast...@asdl.gatech.edu> wrote in message <jshr8b$lbl$1...@newscl01ah.mathworks.com>...
>

> This is the code:
> f = str2func('@(th)isp(n,m,th)');
> th = fsolve(f,0);

Instead of STR2FUNC, I think you'll have to use EVAL:

f = eval('@(th)isp(n,m,th)');

[Alicia]

"Matt J" wrote in message <jsi9nh$ro2$1...@newscl01ah.mathworks.com>...

EVAL worked great! Thank you!