[SOLVED] How to perform element-wise scalar operations on a vector with Scala Breeze?

How to perform element-wise scalar operations on a vector with Scala Breeze?

With Scalala it was possible to perform element-wise operations on a Vector using a scalar operand. Say you have a Vector of random numbers between 0 and 1 and you want to subtract each value from 1:

import breeze.linalg._

val x = DenseVector.rand(5)
val y = 1d :- x  //DOESN'T COMPILE: "value :- is not a member of Double"

Unlike Scalala, Breeze fails to compile with this approach. You can work around this by generating a Vector of ones but it just seems like there should be a better way.

val y = DenseVector.ones[Double](x.size) :- x

Another workaround would be to use the mapValues method which is a bit more readable:

val y = x mapValues { 1 - _ }

What is the proper way to accomplish this with Breeze?

Solution

This is an old question and is sligthly outdated. Currently, with breeze 1.0 and scala 2.11 this syntax is now supported:

import breeze.linalg._

val x = DenseVector.rand(5)
val y = 1d :- x

Output:

import breeze.linalg._
x: breeze.linalg.DenseVector[Double] = DenseVector(0.8274425487378012, 0.11585689753323769, 0.9691257294006741, 0.15061939654911782, 0.8337942418593918)
warning: there was one deprecation warning; re-run with -deprecation for details
y: breeze.linalg.DenseVector[Double] = DenseVector(0.1725574512621988, 0.8841431024667623, 0.030874270599325904, 0.8493806034508822, 0.16620575814060823)