How to add rows and columns dynamically to a Breeze DenseMatrix in Scala

Question

I am hard-coding a matrix with the values below:

val m = breeze.linalg.DenseMatrix((1, 4), (2, 5))
val v = breeze.linalg.DenseMatrix((7, 8), (3, 6))

I want to insert these values on the rows and columns by reading from lists.

And... what's stopping you? What have you tried? Where are you stuck? — The Archetypal Paul, Jan 13 '16 at 08:21
I have gone many of the methods in the documentation which doesn't explain any of the methods properly. Haven't been able to use any method as of now. — aakash singh, Jan 13 '16 at 08:54

score 2 · Answer 1 · answered Jan 13 '16 at 18:24

If you have a rows:Seq[Seq[Double]], where each entry in the outer ~eq is a row:

DenseMatrix(rows:_*)

If you know the matrix dimensions ahead of time, and you have DenseVectors for each row/column)

val dm = DenseMatrix.zeros[Double](rows, cols)
dm(::, c) := myColDenseVector
dm(r, ::) := myRowDenseVector.t

Alternatively, if you have a bunch of DenseVectors, you can say: DenseVector.horzcat(columns:_*)

score 0 · Accepted Answer · edited Feb 27 '16 at 19:02

0

This is what I found out:

val x =  new DenseMatrix(2, 3, Array(11, 12, 13, 21, 22, 23))

which gives the matrix with 2 rows and 3 columns by slicing off the numbers 2 and 3 specified from the array.

The result is:

11  13  22
12  21  23

edited Feb 27 '16 at 19:02

csch

answered Jan 14 '16 at 06:44

aakash singh

2 Answers2