Getting values from 4d matrix according (using) 2d matrix with logical values (0 or 1) - does not work as wanted
4 次查看(过去 30 天)
显示 更早的评论
Hello!
Let say I have a matrix A of dimensions (50*100*248*20) with data and I have another one B (50*100) with logical values (lets image I have 100 of "1") and I want to get values from my 4D matrix according to B. So I am doing
C = A(B);
But then I am getting my values only from A (:,:,1,1) - first page, but I am expecting to get values from all the pages (along all the 3rd and 4 th dimensions). How can I do this?
So I need at the output a matrix with dimensions (100, 1, 248, 20) - which give me 100 values from each page of 248*20
If I am not clear, let me know!, Hoping for you help! Thanks!
6 个评论
madhan ravi
2019-4-4
编辑:madhan ravi
2019-4-4
Indeed sir Walter, thank you for the explanation just noticed the comment.
Linus Olofsson
2020-6-24
编辑:Linus Olofsson
2020-6-24
Could someone please give an example of the explanation Walter gave above? I do not really understand how this is a solution of the problem, nor do I understand the code snippet provided by the earlier comment by Walter.
Could the solution please be explained with my very similar non-functional problem with a 3 channel color image and a 2 dimensional logical array (mask) that I would like to use to color code speficic parts of my image, i.e.:
image = zeros(150,5370,3);
whos mask
Name Size Bytes Class Attributes
mask 150x5370 805500 logical
image(mask,2) = 255; % Change the masked part of the image to be green.
采纳的回答
Yurii Iotov
2019-3-29
3 个评论
Walter Roberson
2019-3-29
I think you mean that Zeros are only to be removed at the edges.
The code I posted here finds the bounding box that contains all of the 1's. It could easily be extended to more dimensions.
更多回答(1 个)
Darren Wethington
2019-3-29
See if this is what you're looking for:
A = rand(10,20,30,40);
B = round(rand(10,20));
four_dim_logical = zeros(size(A));
for i=1:length(four_dim_logical(1,1,:,1))
for j=1:length(four_dim_logical(1,1,1,:))
four_dim_logical(:,:,i,j) = B;
end
end
C = A(logical(four_dim_logical));
dim1 = sum(B(:));
dim2 = 1;
dim3 = size(A,3);
dim4 = size(A,4);
C = reshape(C,dim1,dim2,dim3,dim4);
2 个评论
Darren Wethington
2019-3-29
Just saw solutions in the comments. This solution will be MUCH more computationally expensive if either of those work.
另请参阅
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!