CODEWITHSUNDEEP
matlab
MathematicalPhysicist
MathematicalPhysicist

Reputation: 135

trapz intergation

I have an array of numbers and I want to integrate each column in the array seperatley, and in the end get back an array of numbers after the integration.

I tried "trapz" function but I get a single value, how can i do what I want above?

Here's my code:

t=-1:0.001:1;
x1=100*sinc(100*t);
x2= 100*(sinc(100*t)).^2;
W= -2000*pi:2*pi:2000*pi;
T=-1:0.001:1;
u=x1.*exp(-1i.*W.*t);
v=x2.*exp(-1i.*W.*t);
X11= trapz(t,u);
X22= trapz(t,v);

Thanks in advance.

Upvotes: 0

Views: 403

Answers (1)

Eitan T
Eitan T

Reputation: 32920

If I'm following you correctly, you need u and v to be matrices. For that purpose, you have to resolve two issues in your code:

  1. the ω⋅t product should be a matrix rather than a vector. For that purpose, you need to use matrix multiplication W.' * t (note the added transpose!) and not element-wise multiplication (.*). This produces all the necessary combinations of ω⋅t required for the transform.

  2. In a similar fashion, you need to multiply x by exp(-iωt) column-wise. Use bsxfun instead of the element-wise multiplication, like so:

    u = bsxfun(@times, x1(:), exp(-i * W.' * t));

    The same applies for v.

Since you're using the same exp(-i * W.' * t) both for u and for v, I suggest computing it once and storing it in a variable:

E = exp(-i * W' * t);
u = bsxfun(@times, x1(:), E);
v = bsxfun(@times, x2(:), E);

Following this fix, trapz should produce the desired results now, i.e. X11 and X12 should really be the Fourier Transform applied on x1 and x2, respectively.

Upvotes: 1

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