listing/enumerating numbers

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cgo
cgo 2015-11-10
编辑： Thorsten 2015-11-10
I have the following matrix, named interact:
interact = [1 2;
1 3;
2 1;
2 3;
3 1;
3 4;
4 1]
This matrix means that 1 and 2 interact, 1 and 3 interact, and so on. (just a matrix full of indices.)
Now I want to perform this operation/task.
All that 1 interacts will be added and stored in a matrix. Meaning the interaction between 1 and 2 + interaction between 1 and 3 = interaction of 1.
Similarly, separate matrices for interaction of 2, 3, 4, etc.
How do I do this in matlab?

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Thorsten
Thorsten 2015-11-10
编辑：Thorsten 2015-11-10
for val=1:4
iv{val} = interact(ismember(interact(:,1), val), 2);
end

更多回答（1 个）

Guillaume
Guillaume 2015-11-10
Simply use accumarray:
interact = [1 2; 1 3; 2 1; 2 3; 3 1; 3 4; 4 1];
interactwith = accumarray(interact(:, 1), interact(:, 2), [], @(v) {v})
accumarray uses the subs argument (here your first column) to group together the val argument (here your 2nd column) into a vector which at the end it passes to the fun function argument. Here that function is an anonymous function that just returns the vector as a cell array.

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