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Find value in second column when first column is x

9 次查看（过去 30 天）
Giuseppe Bregliozzi
Hi,
i would like to find the value in a second column corresponding to a value of the first column: [9 0.1; 16 0.2;3 1;89 6;5 0.4;77 0.8]
If I'm searching the value 3 the answer is 1 and if I'm searching 5 the answer is 0.4. I would always search for these numerical values in the first column, but I do not know their row position. Is there an easy and simple wait to do it? Thanks a lot. I have just started using Matlab.

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采纳的回答

Wayne King
Wayne King 2012-3-22
indices = find(A(:,1) == 3);
A(indices,2)
Or
indices = find(A(:,1)>2 & A(:,1) <6);
A(indices,2)
Or
A(find(A(:,1)>2 & A(:,1)<6),2)
Another way is:
locs = ismember(A(:,1), [3 5]);
A(locs,2)

更多回答（1 个）

Geoff
Geoff 2012-3-22
The find function will give you the row numbers. Type:
help find
But if you don't care about the row indices, the preferable way is to use logical indexing:
>> x = [9 0.1; 16 0.2; 3 1; 89 6; 5 0.4; 77 0.8];
>> x(x(:,1)==5, 2)
ans =
0.4

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