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How to create a row that displays the counts of column entries in a matrix using python/sage?

asked 2016-11-09 05:27:10 -0600

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so here is my matrix:

A = matrix([[1,1,2,2,2], 
            [3,1,4,3,3], 
            [0,4,2,4,0], 
            [0,0,2,0,0], 
            [0,0,2,0,0]])

I would like to insert a 0 row that displays the amount of row entries in each column.

This was my original code:

A = matrix([[1,1,2,2,2],
            [3,1,4,3,3],
            [0,4,2,4,0],
            [0,0,2,0,0],
            [0,0,2,0,0]])

puzzle = A.insert_row(0, sum(A)) Whats wrong with this code is that it gives me the sum of each column, when I just need the count of each column.

What I have

[ 4  6 12  9  5]
[ 1  1  2  2  2]
[ 3  1  4  3  3]
[ 0  4  2  4  0]
[ 0  0  2  0  0]
[ 0  0  2  0  0]

Desired

[ 2  3  5  3  2]
[ 1  1  2  2  2]
[ 3  1  4  3  3]
[ 0  4  2  4  0]
[ 0  0  2  0  0]
[ 0  0  2  0  0]
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answered 2016-11-09 15:38:04 -0600

calc314 gravatar image

Here is an option:

r=[Integer(len(A.nonzero_positions_in_column(j))) for j in range(A.dimensions()[1])]
A.insert_row(0, r)
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Nice solution. You could replace A.dimensions()[1]) by A.ncols().

slelievre gravatar imageslelievre ( 2016-11-10 03:50:18 -0600 )edit

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Asked: 2016-11-09 05:27:10 -0600

Seen: 118 times

Last updated: Nov 09 '16