Extracting specific values from a Matrix

Hello,

I have a vector (1x1280; contains indices) and a matrix (1024x1280).

Now I want to extract for each column of the matrix, the value that is at the index contained in my index vector.

This may not be entirely understandable so here is an example:

In the first column of my vector I have the value 450. So I want to know what the value of my matrix in the first column in the row 450 is.

In the second column of my vector I have the value 837. So I want to know what the value of my matrix in the second column in the row 837 is.

And so on.

Thanks a lot

Antonio

Answer 1

[Stephen23]

Use sub2ind:

>> V = randi(1024,1,1280); % fake vector of row indices.
>> M = rand(1024,1280);    % fake matrix of data.
>> S = size(M);
>> X = sub2ind(S,V,1:S(2));
>> Z = M(X);

And checking:

>> Z(1)
ans =  0.40058
>> M(V(1),1)
ans =  0.40058

[Antonio Sarusic]

Thanks