Hello, I have an array of values in "In", I would like to extract the samples in "In" between the indices specified in "SIdx" and "EIdx". SIdx and EIdx are also arrays.

Question

Krishna Ghanakota 2024-3-9

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2092336-hello-i-have-an-array-of-values-in-in-i-would-like-to-extract-the-samples-in-in-between-the-in

评论： Voss 2024-3-9

采纳的回答： Voss

在 MATLAB Online 中打开

I would like to acheive the functionality without using a for loop. Currently the code is written as

Working Code :

In = 1:100;
SIdx = [1 9 33 76];
EIdx = [5 13 42 83];
Out = {};
for i = 1:length(SIdx)
    Out = [Out; {In(SIdx(i):EIdx(i))}];
end

Out =

4×1 cell array

{[ 1 2 3 4 5]}

{[ 9 10 11 12 13]}

{[33 34 35 36 37 38 39 40 41 42]}

{[ 76 77 78 79 80 81 82 83]}

Is there a way to acheive the same functionality without using a for loop.

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Answer 1

Voss 2024-3-9

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https://ww2.mathworks.cn/matlabcentral/answers/2092336-hello-i-have-an-array-of-values-in-in-i-would-like-to-extract-the-samples-in-in-between-the-in#answer_1423026

编辑：Voss 2024-3-9

在 MATLAB Online 中打开

In = 1:100;
SIdx = [1 9 33 76];
EIdx = [5 13 42 83];
siz = zeros(1,2*numel(SIdx)-1);
siz(1:2:end) = EIdx-SIdx+1;
siz(2:2:end) = SIdx(2:end)-EIdx(1:end-1)-1;
Out = mat2cell(In(SIdx(1):EIdx(end)),1,siz).';
Out(2:2:end) = [];
disp(Out)
    {[                    1 2 3 4 5]}
    {[                9 10 11 12 13]}
    {[33 34 35 36 37 38 39 40 41 42]}
    {[      76 77 78 79 80 81 82 83]}

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Krishna Ghanakota 2024-3-9

Very well written code. Thank you.

Voss 2024-3-9

You're welcome!

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Answer 2

Walter Roberson 2024-3-9

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2092336-hello-i-have-an-array-of-values-in-in-i-would-like-to-extract-the-samples-in-in-between-the-in#answer_1423021

在 MATLAB Online 中打开

In = 1:100;
SIdx = [1 9 33 76];
EIdx = [5 13 42 83];
Out = arrayfun(@(S,E) In(S:E), SIdx, EIdx, 'uniform', 0).'
Out = 4×1 cell array
    {[                    1 2 3 4 5]}
    {[                9 10 11 12 13]}
    {[33 34 35 36 37 38 39 40 41 42]}
    {[      76 77 78 79 80 81 82 83]}

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Krishna Ghanakota 2024-3-9

arrayfun(func,A) applies the function func to the elements of A, one element at a time.

The size of "SIdx" can grow very large and I would like to avoid looping.

Is there a way in which "In" can be vector indexed with SIdx and EIdx.

Krishna Ghanakota 2024-3-9

The In, SIdx, EIdx values given in the example code are just for illustrating the idea. These are in actual very large arrays and looping takes quite some time.

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