# How to integral a composite function in yalmip?

3 views (last 30 days)
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.

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 CommentsShow 1 older commentHide 1 older comment
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 on 15 Jul 2019
Get it. Thank you for your kindly help!