Numerical Integral

Hello,

I thought I need to provide more details regarding my question. Below please find a sample code I was running in Matlab 2016a. Here, I am using 'integral2' to calculate the double integral. This function was not available in Compose 2017.3. I try to use 'quad,' but I am not sure whether that function calculated double layer integral. Is there another function that I can use to calculate double layer integral?

clear all;
close all;
clc;

rr1=0.0305;
rr2=0.0415;
xmin=0;
xmax=0.005416836077132;
f = @(x,y) x.^2 + y.^2;
ymin = @(x) sqrt(rr1^2 - x.^2);
ymax = @(x) sqrt(rr2^2 - x.^2);
moment = 2*integral2(f, xmin, xmax, ymin, ymax);
matlab_result=1.5624e-7;
disp(moment);

Thank you

Berker

Hello Berker,

      The best way to implement this in Compose is to nest trapz and quad functions. The following code may help you to solve your issue. 

global rr1;
global rr2;
rr1 = 0.0305;
rr2 = 0.0415;

function q = f(x)
    global rr1;
    global rr2;
    g = @(y) (x*x + y.*y);
    v = [sqrt(rr1^2-x^2):0.000001:sqrt(rr2^2-x^2)];
    q = trapz(v, g(v));
end

xmin = 0;
xmax = 0.005416836077132;
moment = 2*quad(@f, xmin, xmax, [1.0e-10, 1.0e-10])
 

Thanks,

Sijo George

modifying code suggested by @sijo george to run in newer versions of compose 2019.3 or above...

function q = f(x)
    global rr1;
    global rr2;
    n=length(x);
    q=zeros(size(x));
    for j=1:n
        a = sqrt(rr1^2 - x(j)^2);
        b = sqrt(rr2^2-x(j)^2);
        g = @(y)(x(j)^2 + y.^2);
        q(j)=quad(g,a,b);
end
end

xmin = 0;
xmax = 0.005416836077132;
moment = 2*quad(@f, xmin,xmax, [1.0e-10, 1.0e-10])

Thanks,

Manoj kandukuri