Replace the value in the columns of a matrix

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Mario Marinov
Mario Marinov 2015-9-22
评论： Mario Marinov 2015-9-22
In matrix A = [-1 2 3; 4 -5 6; 7 8 -9] order for k1 = 1: size (A, 1) A (k1, find (A (k1,:)> 0, 1, 'first')) = 1 makes replacement of the first positive value in each row 1. If it changes the expression so: for k1 = 1: size (A, 1) A (k1, find (A (k1,:)> 0, 1, 'last')) = 1 will replaced the last positive value in each row. How to do so, to replace the last positive value of 1, but in each column?
  2 个评论
the cyclist
the cyclist 2015-9-22
Is this a homework problem? It seems a bit hard to believe that you could write the code for doing rows, but not understand how to do it for columns.

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回答（1 个）

Kirby Fears
Kirby Fears 2015-9-22
You can switch the loop to iterate over the columns instead of the rows by changing
k1=1:size(A,1)
to
k1=1:size(A,2)
Then switch the indexing of A similarly, changing
A(k1, find (A (k1,:)> 0, 1, 'last'))
to
A(find(A(:,k1)> 0, 1, 'last'),k1)

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