Jacoabian doesn't work

Hello,

I want to calculate

J=jacobian(f_algebr, yss);

But I get Errors. I uploaded my mat file so you can see what f_algebr and yss is.

https://docs.google.com/open?id=0B8e1LayVdzefQkJNekduXy1PNW8

Thank you

[Walter Roberson]

It is faster for us if you tell us what the error message _is_ and which line of code it is on, and if you show us size() and class() of your variables.

[Kim O]

Hi Walter, you are the only one who is answering me. Thank you! :)

Ok here is the error message:

Error using mupadmex

Error in MuPAD command: Invalid variable. [stdlib::diff]

Error in sym/jacobian (line 33)

Jsym = mupadmex('symobj::jacobian',F.s,x.s);

Error in geosim (line 195)

Jac=jacobian(f_algebr, yss);

%---------------------structure of my variables

f_algebr=[exp(x(9)-x(7) ); x(8)*sin(t) ; ....and so on.....]; % ==> : 13x1 sym

yss=[ x(7), x(8), x(9)]; % ==> 1x3 sym

I think matlab has problems with detecting x(*) as a variable in f_algebr...but I don't know how to solve this problem

Thank you Walter for helping me!

Answer 1

[Walter Roberson]

In MuPAD, x(7) is to invoke the function x with argument 7. x[7] would be used to index the vector x at its 7th element.

The simplest way to resolve your difficulty would be to subs() variable names such as x1 for x(1)

Answer 2

[Kim O]

PERFECT simple solution :) Works fine. Thank You!