How do I create every sum of column entries of a m x n matrix?

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Viktor von den Brincken
回答： Viktor von den Brincken 2017-12-27
I would like to create the sums of a mxn matrix that have m summands, one of each row - using a for loop to generate every possible combination. For my 3x3 Matrix A my code would look like this:
for i=1:3
for j=1:3
for k=1:3
S=A(1,i)+A(2,j)+A(3,k);
end
end
end
Now I need this to work for any mxn Matrix. How? Do I need a recursive function or is there any other way?

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采纳的回答

Viktor von den Brincken
Figured another way:
close
clear
clc
A = [1 2 3; 4 5 6;7 8 9];
[Zeile,Spalte] = size(A);
S=MatAdd(A,1);
with
function [Summe] = MatAdd(A,aktuelleZeile)
Summe=[];
[AnzahlZeilen,AnzahlSpalten] = size(A);
if aktuelleZeile==AnzahlZeilen
Summe=A(aktuelleZeile,:)';
else
Summanden=MatAdd(A,aktuelleZeile+1);
for i=1:AnzahlSpalten
Summe=[Summe;Summanden+A(aktuelleZeile,i);];
end
end
end

更多回答（2 个）

Jos (10584)
Jos (10584) 2017-12-19
read the help of sum, and take a look at the dimension argument
help sum
M = randi(10,3,4)
sum(M,1) % sum along rows
  2 个评论
Jos (10584)
Jos (10584) 2017-12-19
O, sorry, I misunderstood your question. So you have n-columns, each with m values (hence the the m-by-n matrix) and you want the sum of the m^n possible combinations ...

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Jos (10584)
Jos (10584) 2017-12-19
A = magic(3)
[m,n] = size(A)
% get the row indices into A for every combination
clear r
[r{n:-1:1}] = ndgrid(1:m)
r = reshape(cat(n+1,r{:}),[],n)
% or use PERMN from the file exchange
% get the columns indices
c = repmat(1:n,size(r,1),1) ;
% transform into linear indices
idx = sub2ind([m,n],r,c) ;
% get the summands for each combination
B = A(idx)
% and sum
out = sum(B,2)

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