How to pick elements of several arrays via assigned vector

2 次查看（过去 30 天）
Warren Chuo
Warren Chuo 2021-6-14
评论： Warren Chuo 2021-6-21
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 个评论
显示 1更早的评论
SALAH ALRABEEI
SALAH ALRABEEI 2021-6-14
what is exactly do you want! How the vec_i is related to the matrix index!
Warren Chuo
Warren Chuo 2021-6-14
编辑：Warren Chuo 2021-6-14
@KSSV
@SALAH ALRABEEI
Thank you for comments.
To make my question more clear:
arr_i = cat(3,arr_i1,arr_i2,arr_i3);
the function(e.g. func_pick) I want to seek is
arr_o = func_pick(arr_i,vec_i);
Detail in/out relationship of this function is:
arr_o(1:2,1) = arr_i(1:2,1,2), since vec_i(1) == 2;
arr_o(1:2,2) = arr_i(1:2,2,3), since vec_i(2) == 3;
arr_o(1:2,3) = arr_i(1:2,3,1), since vec_i(3) == 1;
arr_o(1:2,4) = arr_i(1:2,4,2), since vec_i(4) == 2;

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Shivam Malviya
Shivam Malviya 2021-6-15
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)
  1 个评论
Warren Chuo
Warren Chuo 2021-6-21
Hi, Shivam Malviya,
Thank you for your wise input, and I'm very sorry to respond this late.
Somebody suggested me 'sub2ind' and manipulate indices instead of values.
After few optimizing steps, I found out a straightforward way to just cover my real issues efficiently.
Your suggested function can lead to expected result very well.
Just I need few moment to digest the arithmetic relationship inside this function.
Anyway, your input is very appreciated.

请先登录，再进行评论。

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Descriptive Statistics 的更多信息

标签

产品


版本

R2010b

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by