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How to integral a composite function in yalmip?

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Tong Liu
Tong Liu on 13 Jul 2019
Commented: Tong Liu on 15 Jul 2019
sdpvar x1 x2 x3 u1
% syms x1 x2 x3 u1
d=x1+x2;
y=x1+x2+u1+d;
z=y+3;
t=int(z,y,0,y)
hello everyone...I have define a integration by yalmip, but there are some error..
If replace by syms, there are still errors.
Could you please help me find the mistakes? THANKS.

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Accepted Answer

infinity
infinity on 13 Jul 2019
Hello,
You define z as a function of x1, x2, and u1. But, you apply the integral function to compute the integral of z over the interval [0, y] and told the integral function that the variable of z is also y. It is not correct.
Let image that what you are doing like trying to compute

  3 Comments

Tong Liu
Tong Liu on 15 Jul 2019
Thank you for your answer. As you know, z is also a function of y. Why can't I intergral according to y directly? Is that only the final variable like x and u can be used for integration?
Thanks!
infinity
infinity on 15 Jul 2019
Hello,
In case, we have function z(y) = y + 3 then we can compute the integral of z with respect to y as simple by
syms y a
z = y + 3;
res = int(z,y,0,a)
where "a" is upper limit of the integral.
But, in your given code, you defined z as function of x1, x2, u1 and parameter d. Matlab can not understand that z is a function y.
Tong Liu
Tong Liu on 15 Jul 2019
Get it. Thank you for your kindly help!

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