How to pick elements of several arrays via assigned vector
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Warren Chuo
on 14 Jun 2021
Commented: Warren Chuo
on 21 Jun 2021
Hi,
I have 3 arrays, and would like to form new array picking elements from these 3 arrays.
The picking is via my assigned vector.
The computation should be matrix computation, no for loop inside.
e.g.
-----
[input]
arr_i1 = [111,112,113,114; ...
121,122,123,124];
arr_i2 = [211,212,213,214; ...
221,222,223,224];
arr_i3 = [311,312,313,314; ...
321,322,323,324];
vec_i = [2,3,1,2];
[output]
arr_o = [211,312,113,214; ...
221,322,123,224];
-----
Your answer would be quite appreciated.
3 Comments
SALAH ALRABEEI
on 14 Jun 2021
what is exactly do you want! How the vec_i is related to the matrix index!
Accepted Answer
Shivam Malviya
on 15 Jun 2021
Hi Warren!
You can find the implementation of the func_pick function below: -
func_pick.m
function arr_o = func_pick(arr_i, v)
d3 = v;
d2 = 1:length(d3);
d1 = [1:size(arr_i, 1)]';
i1 = repmat(d1, 1, length(d2));
i2 = repmat(d2, length(d1), 1);
i3 = repmat(d3, length(d1), 1);
i123 = cat(3, i1, i2, i3) - 1;
linear_i = i123(:, :, 1) + size(arr_i, 1) * (i123(:, :, 2) + size(arr_i, 2) * i123(:, :, 3)) + 1
arr_o = arr_i(linear_i);
end
script.m
a1 = [111,112,113,114;
121,122,123,124];
a2 = [211,212,213,214;
221,222,223,224];
a3 = [311,312,313,314;
321,322,323,324];
arr_i = cat(3, a1, a2, a3);
v = [2, 1, 3, 2];
arr_o = func_pick(arr_i ,v)
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