How to retrieve specific rows that the coordinates x,y have been saved in another matrix?

Hi,

I have a data matrix Data(8765x138) that first and second columns are x and y coordinates. I have sampled some specific points in another array, Points(2000x2), first and second columns in A refers to x and y, respectively. I want to extract some specific rows in Matlab that match with matrix A (both x,y). The output should be (2000x138). I tried the following code but the result is not correct.

      newData = Data(ismember(Data(:,1),Points(:,1))& ismember(Data(:,2),Points(:,2)),:);

what should I do to select the rows from Data that its first and second columns match to my Points matrix. Someone please help, I feel like I've tried everything!

Answer 1

[Guillaume]

The problem with your statement is that it finds all rows of Data whose x match an x in Points and match any y in Points but not necessarily in the same Points row. To fix this, you need to use the 'row' option of ismember:

newData = Data(ismember(Data(:, [1 2]), Points(:, [1 2]), 'rows'), :)

[Sara Salimi]

Dear Guillaume, Thank you very much. it works but why the number of rows in newData is not equal to the number of rows in Points Matrix?!

[Guillaume]

I see now reasons why the two should be equal unless each row of Points is present and present only once in Data.