extract data from a 3D matrix using a window

I'd like to extract data along the 3rd dimension of a 3D matrix with the size of 2*2*10 using a window with a fixed size but a variable start indeces. But it doesn't work.

Script:

clc; clear;

a = 1:10; % 1*10 vector

J = reshape(repelem(a,2,2),2,2,length(a)); % expand a to 2*2*10 matrix

wsize = 5; % window size

startInd = [1,2;3,4]; % start index of the window

Q = J(:,:,startInd:startInd+wsize); % cannot extract accurately !!!

Answer 1

[Mathieu NOE]

hello

there is one Q array per startInd value so either you use Q in a for loop without indexing (if you can tolerate to overwrite Q at each iteration, or store each result separately as shown below :

and also correct startInd dimensions as it should be a 1D vector

a = 1:10; % 1*10 vector
J = reshape(repelem(a,2,2),2,2,length(a)); % expand a to 2*2*10 matrix
wsize = 5; % window size
startInd = [1 2 3 4]; % start index of the window

for k = 1:numel(startInd)
    disp(['-- Iteration index k = ' num2str(k) '--'])
    Q = J(:,:,startInd(k):startInd(k)+wsize) % yes you can
    % if you want to store each result separately
    Qstore{k} = Q; 
end  

-- Iteration index k = 1--

Q = 
Q(:,:,1) =

     1     1
     1     1


Q(:,:,2) =

     2     2
     2     2


Q(:,:,3) =

     3     3
     3     3


Q(:,:,4) =

     4     4
     4     4


Q(:,:,5) =

     5     5
     5     5


Q(:,:,6) =

     6     6
     6     6

-- Iteration index k = 2--

Q = 
Q(:,:,1) =

     2     2
     2     2


Q(:,:,2) =

     3     3
     3     3


Q(:,:,3) =

     4     4
     4     4


Q(:,:,4) =

     5     5
     5     5


Q(:,:,5) =

     6     6
     6     6


Q(:,:,6) =

     7     7
     7     7

-- Iteration index k = 3--

Q = 
Q(:,:,1) =

     3     3
     3     3


Q(:,:,2) =

     4     4
     4     4


Q(:,:,3) =

     5     5
     5     5


Q(:,:,4) =

     6     6
     6     6


Q(:,:,5) =

     7     7
     7     7


Q(:,:,6) =

     8     8
     8     8

-- Iteration index k = 4--

Q = 
Q(:,:,1) =

     4     4
     4     4


Q(:,:,2) =

     5     5
     5     5


Q(:,:,3) =

     6     6
     6     6


Q(:,:,4) =

     7     7
     7     7


Q(:,:,5) =

     8     8
     8     8


Q(:,:,6) =

     9     9
     9     9

Qstore{k}

ans = 
ans(:,:,1) =

     4     4
     4     4


ans(:,:,2) =

     5     5
     5     5


ans(:,:,3) =

     6     6
     6     6


ans(:,:,4) =

     7     7
     7     7


ans(:,:,5) =

     8     8
     8     8


ans(:,:,6) =

     9     9
     9     9