How to extract value from a matrix with given indices

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Shin
Shin 2023-1-17
评论： Shin 2023-1-17
Hi there,I have a an array of index and a matrix such as
index = [2 4 3 1 5];
matrix = [5 2 5 3 4;
1 2 4 2 6;
7 5 0 9 3;
6 6 3 1 2;
3 6 8 2 7];
How can I extract the value from each column of the matrix with the given index to obtain a new array such as
new = [1 6 0 3 7];
Thanks.
-Shin-

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采纳的回答

Dyuman Joshi
Dyuman Joshi 2023-1-17
Ran in:
index = [2 4 3 1 5];
matrix = [5 2 5 3 4;
1 2 4 2 6;
7 5 0 9 3;
6 6 3 1 2;
3 6 8 2 7];
s=size(matrix);
new=matrix(sub2ind(s,index,1:s(2)))
new = 1×5
1 6 0 3 7

更多回答（2 个）

Abhinav
Abhinav 2023-1-17
编辑：Abhinav 2023-1-17
index = [2 4 3 1 5];
matrix = [5 2 5 3 4;
1 2 4 2 6;
7 5 0 9 3;
6 6 3 1 2;
3 6 8 2 7];
new=[];
for i=1:length(index)
new(i)=matrix(index(i),i);
end
new
  1 个评论
Shin
Shin 2023-1-17
Hi Abhinav, thank for the solution, however the code only display the last value with is "new = 7" in this case. After I modify a little on your code and I'm able to get all the value. Code as below.
index = [2 4 3 1 5];
matrix = [5 2 5 3 4;
1 2 4 2 6;
7 5 0 9 3;
6 6 3 1 2;
3 6 8 2 7];
indexNO = 5;
new = zeros(1,indexNO);
for i = 1:indexNO
new(1,i) = matrix(index(i),i);
end
new
Anyway, thanks again for you solution.

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prasanth s
prasanth s 2023-1-17
code example is
ind = sub2ind(size(matrix),index,1:5);
new=matrix(ind)

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