First of all Mahout's Math-Scala DSL, is really nice. I can write
really compact code.
Here is a my problem description ( i referred to [1] ).
First I import all the required classes in Scala REPL:
import org.apache.mahout.math.{ Vector => MahoutVector }
import org.apache.mahout.math.scalabindings._
import org.apache.mahout.math.DenseMatrix
import scala.util.Random
import org.apache.mahout.math.Matrix
import Math.min
import RLikeOps._
Then I create a matrix
scala> val a = dense((1, 2, 3), (3, 4, 5))
a: org.apache.mahout.math.DenseMatrix =
{
0 => {0:1.0,1:2.0,2:3.0}
1 => {0:3.0,1:4.0,2:5.0}
}
Appply the function using a loop:
scala> for(r <- 0 until a.numRows; c <- 0 until a(r,::).size) { a(r,c)
= Math.log(a(r,c)) }
warning: there were 1 deprecation warnings; re-run with -deprecation for details
The resulting matrix
scala> a
res35: org.apache.mahout.math.DenseMatrix =
{
0 => {1:0.6931471805599453,2:1.0986122886681098}
1 => {0:1.0986122886681098,1:1.3862943611198906,2:1.6094379124341003}
}
I want to apply an arbitrary function ( such as Math.log, or a
function defined by me ), to a matrix or vector withoug using any
loops. This is possible in Octave/Matlab as described here [2].
How can I do this in Mahout using Scala DSL ?
Thanks in advance.
Regards,
Saleem
[1] https://mahout.apache.org/users/sparkbindings/home.html
[2]
http://stackoverflow.com/questions/2470844/loopless-function-calls-on-vector-matrix-members-in-matlab-octave
