How do I split an array into small array of fixed size with increments by 1?

Question

Alekhya Hati 2022-10-28

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https://ww2.mathworks.cn/matlabcentral/answers/1838048-how-do-i-split-an-array-into-small-array-of-fixed-size-with-increments-by-1

评论： Bruno Luong 2022-10-28

采纳的回答： Bruno Luong

For example, I have an array, say

aa = [2 5 6 10 2 4 2 1 -1 -12 0 3 7];

What I want to do is create arrays of length 4, such as

[2 5 6 10], [5 6 10 2], [6 10 2 4], [10 2 4 2], [2 4 2 1], [4 2 1 -1], ....

and group them into a matrix. I understand this can be done in a for loop, but is there a way to vectorize this process?

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Answer 1

Bruno Luong 2022-10-28

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在 MATLAB Online 中打开

A=randi(10,1,10)
A = 1×10
     3    10     1     4     8     8     9     3    10     6
k=4;
B = hankel(A(1:end-k+1),A(end-k+1:end))
B = 7×4
     3    10     1     4
    10     1     4     8
     1     4     8     8
     4     8     8     9
     8     8     9     3
     8     9     3    10
     9     3    10     6

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Alekhya Hati 2022-10-28

编辑：Alekhya Hati 2022-10-28

在 MATLAB Online 中打开

I found another method as well later on that worked for me

aa = [2 5 6 10 2 4 2 1 -1 -12 0 3 7];
bb = buffer(aa, 4, 3, 'nodelay')
bb = 4×10
     2     5     6    10     2     4     2     1    -1   -12
     5     6    10     2     4     2     1    -1   -12     0
     6    10     2     4     2     1    -1   -12     0     3
    10     2     4     2     1    -1   -12     0     3     7

Bruno Luong 2022-10-28

I never use this command buffer, so I learn something.

It requires the signal processing toolbox though.

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Answer 2

DGM 2022-10-28

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编辑：DGM 2022-10-28

在 MATLAB Online 中打开

I'm sure there are other ways, but here's one way.

% the input
A = [2 5 6 10 2 4 2 1 -1 -12 0 3 7];
% the parameter
blocklen = 4;
% generate a 2D array of indices
nrows = numel(A)-blocklen+1;
idx = (1:blocklen) + (0:nrows-1).';
% build the output by direct addressing
B = A(idx)
B = 10×4
     2     5     6    10
     5     6    10     2
     6    10     2     4
    10     2     4     2
     2     4     2     1
     4     2     1    -1
     2     1    -1   -12
     1    -1   -12     0
    -1   -12     0     3
   -12     0     3     7