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

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vx2008
vx2008 el 15 de Dic. de 2015
Comentada: Guillaume el 15 de Dic. de 2015
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).

Respuesta aceptada

Guillaume
Guillaume el 15 de Dic. de 2015
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))

Más respuestas (1)

Stephen23
Stephen23 el 15 de Dic. de 2015
Editada: Stephen23 el 15 de Dic. de 2015
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 comentario
Guillaume
Guillaume el 15 de Dic. de 2015
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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