How to: map selected entries of one matrix to entries of a second?
3 views (last 30 days)
Show older comments
Anthony Azevedo
on 2 Apr 2018
Commented: Anthony Azevedo
on 2 Apr 2018
I have a matrix, A, of 1024x1280 elements(an image), and I have two mapping matrices, Row_map (670 X 1428) and Col_map (670 X 1428), that take element Row_map(1,1), Col_map(1,1) of A (i.e. element A(4,892) where Row_map(1,1)=4, Col_map(1,1)=892) and put that value into matrix R(1,1), where elements of R are a rotated subset of values in A. R is also 670 X 1428, and some entries of Row_map, Col_map and R are nans. (Specifically, it's just the corner of the image, rotated an arbitrary angle, but I think that's beside the point). Once I have this mapping, I will go through a series of matrices like A (a video), and perform the same mapping.
Currently I'm doing the silly thing of looping over row and column indices of Row_map and Col_map to enter each value of R. There has to be a more efficient way, but I'm blanking right now. Really appreciate your help.
0 Comments
Accepted Answer
More Answers (1)
KSSV
on 2 Apr 2018
Read about sub2ind, ind2sub.
R = NaN(size(Row_map)) ;
idx = sub2ind(size(A), Row_map(:),Col_map) ;
R(idx) = A(idx) ;
1 Comment
See Also
Categories
Find more on Resizing and Reshaping Matrices in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!