extracting the index of an irregular line on a 2D matrix

Hi.

I have a 2D matrix and a vector which passes through some samples of this matrix irregularly. The vector values ​​shows the Y values ​​of the samples it passes through. I want to extract the index of each sample of this vector roughly. In other words, I want to know the corresponding index number of each vector sample, in the matrix. Please find attached the image. The vector values ​​are shown in white line passes throgh the 2D matrix (image).

Any suggestions?

Thanks.

Answer 1

[KSSV]

Read about ismember.

A = rand(10) ; 
B = A(randperm(100,10)) ; 
[c,ia] = ismember(A(:),B) ;
A(c) 

[KSSV]

You can also use knnsearch.

[hamed]

Thanks @KSSV

I am not sure if knnsearch works in this contexts. Let me elaborate more.

I have a 250 * 530 matrix (A). In this matrix, X-axis shows location, and Y axis shows time.

I also have a vector (V) of 1* 530 whose elements are time. I want to find the index for example V(200) which has a value of 1200 milisecond and is on the 200th column of A. Axtually I know the column number (200), but do not know the best index in is related to.

Sorry if it is naive.

[KSSV]

So you have X,Y location data and Z data. Where X is position and Y is time. Now you have some time step t which belongs to Y; You want to find the X index for that? IS it so?

[hamed]

Exactly.

I thouth a way is to fix the time values in Y (vector V), substract them from the surface time (1650). So I have the Y sample in each X. Then using sub2ind, the index is estimated.

[KSSV]

Do you have the respective Z value of t?

[hamed]

No

[KSSV]

Then how you expect to extract? For every given t, we will get a complete column of x.