# Use forLoop to manipulate values of elements in a specific column

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JZ 2015년 12월 5일
댓글: lsutiger1 2015년 12월 6일
I created the following 5x5 matrix with no data:
mat = zeros(5:5)
mat =
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
I would like to use a for loop to generate the following result
mat =
0 0 0 0 0
0 0 0 10 0
0 0 0 20 0
0 0 0 30 0
0 0 0 40 0
I attempted using the following code, but the operation was performed on the first column - not the 4th, as I had intended.
for i = 2:length(mat(:,4))
mat(i) = mat(i-1) + 10;
end
This was the actual result
mat =
0 0 0 0 0
10 0 0 0 0
20 0 0 0 0
30 0 0 0 0
40 0 0 0 0
I imagine this is a simple syntax problem, but I am not finding the solution in any of the forums. Any help is appreciated.
Thanks

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### 채택된 답변

Star Strider 2015년 12월 5일
This works:
mat = zeros(5:5);
mat(:,4) = 0:10:10*(size(mat,1)-1);
mat =
0 0 0 0 0
0 0 0 10 0
0 0 0 20 0
0 0 0 30 0
0 0 0 40 0
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Star Strider 2015년 12월 5일
My pleasure!

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### 추가 답변(1개)

lsutiger1 2015년 12월 5일
You have only specified the row that you want to manipulate; you need to specify both the row and column.
mat(i) = mat(i-1,4) + 10;
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lsutiger1 2015년 12월 6일
That's because you used i-4 rather than i-1.

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