how to do this calculation not by 'for' cycle?

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vx2008
vx2008 2015-12-15
评论： Guillaume 2015-12-15
I have the below data:
data =[...
1.0000 1.0000 1.0000 53.1100;...
1.0000 2.0000 2.0000 59.0900;...
2.0000 1.0000 2.0000 71.3100;...
2.0000 2.0000 1.0000 70.2400]
Now I want to get a 'variable'--Data as below:
Data=[53.11+59.09 53.11+71.31 53.11+70.24;
71.31+70.24 59.09+70.24 59.09+71.31]
I can get 'Data' by 'for' cycle function but I want to do this work by other better method.
The addition logic is that:
take column 2 of data for example, both data(1,2) and data(3,2) equal 1.0000, so add data(1,4) and data(3,4) to get Data(1,2).

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采纳的回答

Guillaume
Guillaume 2015-12-15
One possible way to do it:
data = [1 1 1 53.1100
1 2 2 59.0900
2 1 2 71.3100
2 2 1 70.2400];
%first split data into two matrices for easier referencing:
rowdest = data(:, 1:end-1);
rowvals = data(:, end);
%second create matrix of column indices
coldest = repmat(1:size(rowdest, 2), size(rowdest, 1), 1);
%third use accumarray to compute the sum:
newdata = accumarray([rowdest(:) coldest(:)], repmat(rowvals, size(rowdest, 2), 1))

更多回答（1 个）

Stephen23
Stephen23 2015-12-15
编辑：Stephen23 2015-12-15
This is easy using accumarray:
inp = [1,1,1,53.1100;1,2,2,59.0900;2,1,2,71.3100;2,2,1,70.2400]
out(:,3) = accumarray(inp(:,3),inp(:,4));
out(:,2) = accumarray(inp(:,2),inp(:,4));
out(:,1) = accumarray(inp(:,1),inp(:,4))
and the result is:
out =
112.20 124.42 123.35
141.55 129.33 130.40
and your example output is:
>> [53.11+59.09,53.11+71.31,53.11+70.24;71.31+70.24,59.09+70.24,59.09+71.31]
ans =
112.20 124.42 123.35
141.55 129.33 130.40
  1 个评论
Guillaume
Guillaume 2015-12-15
If data is always three columns of indices + one column of number, this works. If the size of data is not fixed, my answer is more generic.

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