Matrix Row manipulation in Breeze using Scala?

Question

I've a DenseMatrix

1  2  3  0   0   0   0    0    0    
0  0  0  11  22  33  0    0    0    
0  0  0  0   0   0   111  222  333

I want to remove the first row and then a last row with all 0s

0  0  0  11  22  33  0    0    0    
0  0  0  0   0   0   111  222  333 
0  0  0  0   0   0   0    0    0

How do I achieve this in Breeze ?

Have you looked at Saddle (https://github.com/saddle/saddle) as a replacement for Breeze? — wheaties, Apr 22 '14 at 12:51
@wheaties, I'm curious to know what you like about Saddle over Breeze. I'd like to know how I can make Breeze better. — dlwh, Apr 22 '14 at 19:02

score 3 · Accepted Answer · answered Apr 22 '14 at 18:23

3

First, gather the rows you still want:

val subset = matrix(::, 2 to 3)

then add the zeroes:

val newMatrix = DenseMatrix.horzcat(subset, DenseMatrix.zeros[Double](1,9))

I might have mixed up rows and columns in the last line.

answered Apr 22 '14 at 18:23

Reactormonk

1 Answers1