create matrix with integral

Question

Mohammed Hachemi 2019-9-15

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/480454-create-matrix-with-integral

回答： Mohammed Hachemi 2019-9-15

Hello

I need your help , I am beginner in matlab and want to use matlab to calculate integral and create matrix with variable n and m.

x = [-1,1]

∫ (f(x,n)*f(x,m)dx

I want to creat matrix

f(x,1)*(f(x,1)     f(x,1)*(f(x,2)    .....
f(x,2)*(f(x,1)     f(x,1)*(f(x,1)  
.
.

I try this code but I need your help to create one

P = 5;   exemple 
fun(1) =@(x)(1-x)/2;
fun(2) =@(x)(1+x)/2;
fun(n) =@(x) sin(pi/2*(n-1).*(1+x)); if n >= 2;
for m = 1:P;
    for n = 1:P;
        L[n,m]=integral((fun(m).*fun(n)),-1,1,-1,1);
    end
end 

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Answer 1

Walter Roberson 2019-9-15

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/480454-create-matrix-with-integral#answer_391966

在 MATLAB Online 中打开

P = 5; 
for m = 1:P;
    for n = 1:P;
        L(n,m) = integral( @(x) fun(x,n).*fun(x,n)), -1, 1);
    end
end
function y = fun(x, n)
%warning: x will be a vector or array!
  if n == 1
     y = (1-x)/2;
  elseif n == 2
     y = (1+x)/2;
  else 
     y = sin(pi/2*(n-1).*(1+x));
  end