Asked by Jaime
on 4 Mar 2013

Hello, i must say that im not really good programing with matlab, i have this problem (i´ll explain it very fast):

1º I made a function that give me a vector made of real numbers i(1,6). 2º With that vector i, i would like to build and solve the next system:

f(1)= x(1)*x(2)*x(3)-i(1); f(2)= x(1)*x(6)*x(3)-i(2); f(3)= x(5)*x(2)*x(3)-i(3); f(4)= x(5)*x(6)*x(3)-i(4); f(5)= x(4)*x(2)*x(3)-i(5); f(6)= x(4)*x(6)*x(3)-i(6);

For doing it, i tried the suggestion in this video:

http://www.youtube.com/watch?v=yN4gMygK8Uw

And if i do it, giving constant values to i (instead of using the vector i), i can solve the system, but when i introduce i, matlab says: undefined variable i... and several more errors.

I hope that everybody can understand what i mean, and i would be really gratefull if you can help me with it. Thanks you very much!

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Answer by Brian B
on 4 Mar 2013

Edited by Brian B
on 4 Mar 2013

Accepted answer

`fsolve` will only pass in a single argument, so `i` will be undefined. Assuming you want to solve this equation for fixed values of `i` (say `i = ibar`) you can use an anonymous function like this:

ibar = (1:6); ecuaciones_con_i = @(x) ecuaciones(x, ibar);

Then pass `ecuaciones_con_i` to fsolve (without a @, since it is already a function handle):

xbar = fsolve(ecuaciones_con_i, x0);

Jaime
on 4 Mar 2013

it worked very well now!, thanks you very much, you saved me! :p

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## 2 Comments

## Brian B (view profile)

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/65826-how-do-i-solve-this-non-linear-system#comment_134007

Can you post more of your code?

## Jaime (view profile)

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/65826-how-do-i-solve-this-non-linear-system#comment_134009

check this link: http://www.mathworks.es/es/help/optim/ug/fsolve.html

I want to do exactly the same as in example 1(scroll down after opening), but my problem is that myfun.m file looks like this:

as you see, for building my system i also need i, not only x. So when i call it with fsolve it doesn´t work.