Usings subs on matrices ?

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Matthieu 2013-10-31

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评论： Matthieu 2013-10-31

Hi everyone,

I'm trying to substitute variables in a matrix, but I run in something a little bit weird. When using the command "C = subs(C, exp1, exp2)", the result is not the matrix that I would have had if I had done the same substitution for all elements of C. How can it be ?

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Jos (10584) 2013-10-31

编辑：Jos (10584) 2013-10-31

Your question is too vague. Can you give a very small example of

your input
what you did
what you got as output
what you expected to get

Added: I do not know a command called SUBS

Matthieu 2013-10-31

Hi Jos,

So my matrix C was 5x5 matrix with quite complicated expression, but to make it simple let's say that all coefficients are of the form : (xi - xj) * lp * exp where exp is a symbolic expression, xi (i=1:5) and lp are symbolic variables.

Now, I have a variable y which value is 0 and my script goes :

C = subs(C, xi, y);

which I would expect to give -xj * lp * exp, but what I actually get is lp. When I do the substitution on the expression only, I get, the right result.

Any idea ?

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