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.

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.

Answer 1

[Voss]

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]}

[Krishna Ghanakota]

Very well written code. Thank you.

[Voss]

You're welcome!

Answer 2

[Walter Roberson]

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]}

[Krishna Ghanakota]

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]

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.