Integrating and substituting

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Mark
Mark 2012-6-21
So I have a long code and now I want to differentiate a formula, y, with respect to x in and integral 0 to t. However, I want to keep the previous x for more calculation and substitute my x. Howe do I do this? Example:
x=5;
syms x
int(y,x,0,t)
I'm convinced I keep to substitue, using sub(), but I am unsure how tis would work out because x is now a plain variable (from syms). Any ideas?

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Walter Roberson
Walter Roberson 2012-6-21
Write y in terms of a different symbol, such as X, and
subs(y, X, sym('x'))
to get y in terms of the symbol x (distinct from your variable "x")
Or is y a string instead of a symbolic expression? If it is, then you should be able to do
int(y, 'x', 0, t)
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Mark
Mark 2012-6-26
I should have accepted this answer long ago. It was spot on!

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