# Numerical integration of double integrals in MAtlab

Asked by Himanshu on 9 Mar 2011
Latest activity Commented on by Walter Roberson on 9 Mar 2011

Hi,

I am trying to integrate an array of numbers in polar co-ordinates. I do not have a defined function for this array of numbers. How can I integrate the array of numbers numerically in matlab? Theta goes from 0 to 2*pi and R goes from 0 to 10.

Thank you, HT

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Answer by Matt Fig on 9 Mar 2011

Look at the TRAPZ function.

Walter Roberson on 9 Mar 2011

That sounded okay at first, under the assumption that the polar was converted to cartesian, but then I realized that in polar plots it is common for the same X cartesian coordinate to have multiple Y, which is a situation that trapz is not designed to handle.

Andrew Newell on 9 Mar 2011

It depends on what the problem is. If the problem is to integrate inside a curve on a polar plot, you're right. But I think the problem is really just to integrate a function like sin(x) given a set of values [x sin(x)].

Walter Roberson on 9 Mar 2011

Andrew, the OP stated that theta goes from 0 to 2*pi; as the range is greater than Pi, there must be overlapping X areas.