# Efficient Way to find index of max column for each row

조회 수: 50 (최근 30일)
Varsha 2022년 7월 12일
답변: Anay Aggarwal 2022년 7월 12일
Hey I've an matrix of size n x m. I want to find the index of max_col corresponding to each row. I know, i can use a loop to check but is there any other efficient way to do that?

댓글을 달려면 로그인하십시오.

### 답변 (4개)

Les Beckham 2022년 7월 12일
편집: Les Beckham 2022년 7월 12일
Are you wanting to find the column number of the maximum value in each row? If so, this is how you can do that:
A = magic(5) % example data
A = 5×5
17 24 1 8 15 23 5 7 14 16 4 6 13 20 22 10 12 19 21 3 11 18 25 2 9
[m, idx] = max(A, [], 2) % max value from each row and column number where the max value occurs
m = 5×1
24 23 22 21 25
idx = 5×1
2 1 5 4 3
If not, please clarify what you are trying to do.
##### 댓글 수: 0이전 댓글 -2개 표시이전 댓글 -2개 숨기기

댓글을 달려면 로그인하십시오.

Keshav 2022년 7월 12일
Hi, Based on my understanding you have a matrix. for each row you want to find the index of maximum value. you can use the below code to do that.
x = [1 2 3; 5 3 4;10 8 9]
[mx,idx] = max(x,[],2)
here idx(i) will represent the index of column with max value in ith row.
##### 댓글 수: 0이전 댓글 -2개 표시이전 댓글 -2개 숨기기

댓글을 달려면 로그인하십시오.

Harshit Gupta 2022년 7월 12일
Hi, I understand that you're trying to find an efficient way to find the maximum values in each row.
You can do this simply with the max() function on the matrix without using a for loop.
Here's an example:
M=[2 4 0 1;12 3 5 2;7 10 4 1;3 5 20 7]
[max_values, idx] = max(M') %row maximums
You can even get the column maximums and the maximum value of the matrix
[max_values, idx] = max(M) %col maximums
[matrix_max, idx] = max(M(:)) %matrix maximum
Hope this helps!
##### 댓글 수: 0이전 댓글 -2개 표시이전 댓글 -2개 숨기기

댓글을 달려면 로그인하십시오.

Anay Aggarwal 2022년 7월 12일
Hi Varsha,
I have an understanding that you want to find the column number of maximum element in each row of a matrix.
You can perform the following operation:
x = [1 2 3; 4 50 6;11 8 9]
x = 3×3
1 2 3 4 50 6 11 8 9
[mx,idx] = max(x,[],2)
mx = 3×1
3 50 11
idx = 3×1
3 2 1
Hope this helps
Regards

댓글을 달려면 로그인하십시오.

### 카테고리

Help CenterFile Exchange에서 Logical에 대해 자세히 알아보기

### Community Treasure Hunt

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

Start Hunting!

Translated by