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matlabsymbolic-math

symbolic substitution in Matlab

The function subs in matlab does not work as expected with me. I define a symbolic variable, then assign it a value of 0, but later I discover it has not been assigned anything.

syms x1
a=x1
subs(a,x1,0)
a

produces

x1

and not 0. Any ideas?

Solution

  • From my documentation for MATLAB:

    subs(s,old,new) returns a copy of s replacing all occurrences of old with new, and then evaluating s.

    subs doesn't modify a, it returns a modified version of it. For example, try this:

    syms x1;
a = x1;
b = subs(a,x1,0);
a
b

    Returns

    a = x1
b = 0