How to avoid for loop when indexing?

2018 7 2
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回答已采纳
更新时间：2018 7 2
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Hello,
I have the following for loop, where pairs(500x10), is there to calculate cc without for loop?
for i=1:500
cc(i,:)=pairs(i,pairs(i,:));
end

4 个评论
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Stephen23
Stephen23 2018-7-2
@Mantas Vaitonis: what is pairs2 ? What values do pair and pairs2 contain?
Mantas Vaitonis
Mantas Vaitonis 2018-7-2
编辑：Mantas Vaitonis 2018-7-2
Sorry, tehre was mistake, both are pairs, they contain double type values like [1 5 4 3 5].
Stephen23
Stephen23 2018-7-2
@Mantas Vaitonis: given that pairs contains non-integer values, what do you expect
pairs(i,pairs(i,:));
to do?
Mantas Vaitonis
Mantas Vaitonis 2018-7-2
Those values suppose to be integer, i fixed my commnet, and should return valuse by index stored in pairs.

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 采纳的回答

Jan
Jan 2018-7-2
编辑：Jan 2018-7-2

0 个投票

s = size(pairs);
index = sub2ind(s, repmat((1:s(1)).', 1, s(2)), pairs)
cc = pairs(index)

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Mantas Vaitonis
Mantas Vaitonis 2018-7-2
Unfortunately, it is not what I am looking for. With Your code if I have pairs [5 1 4 5 1], cc should be [1 5 5 1 5] and the result with your code is [4 5 2 4 5].
Jan
Jan 2018-7-2
编辑：Jan 2018-7-2
pairs = [5 1 4 5 1];
s = size(pairs);
index = sub2ind(s, repmat((1:s(1)).', 1, s(2)), pairs)
cc = pairs(index)
cc =
1 5 5 1 5
I don't know why you get [4 5 2 4 5]. Please try it again.
Mantas Vaitonis
Mantas Vaitonis 2018-7-2
Maybe I did mistake when copying your code, now it did work, thank you.

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