ScalaのBreezeを使って行列計算

自分用メモ

sbtプロジェクトの準備

scalanlp/breeze

mkdir breeze_test
cd breeze_test
touch build.sbt

build.sbt

libraryDependencies  ++= Seq(
  // Last stable release
  "org.scalanlp" %% "breeze" % "0.12",

  // Native libraries are not included by default. add this if you want them (as of 0.7)
  // Native libraries greatly improve performance, but increase jar sizes. 
  // It also packages various blas implementations, which have licenses that may or may not
  // be compatible with the Apache License. No GPL code, as best I know.
  "org.scalanlp" %% "breeze-natives" % "0.12",

  // The visualization library is distributed separately as well.
  // It depends on LGPL code
  "org.scalanlp" %% "breeze-viz" % "0.12"
)


resolvers += "Sonatype Releases" at "https://oss.sonatype.org/content/repositories/releases/"

sbt update
> console
scala>

行列計算してみる

scala> import breeze.linalg._

scala> val m1 = DenseMatrix((1,2), (3,4))
m1: breeze.linalg.DenseMatrix[Int] =
1  2
3  4

scala> val m2 = DenseMatrix((5,1), (4,8))
m2: breeze.linalg.DenseMatrix[Int] =
5  1
4  8

scala> m1 + m2
res0: breeze.linalg.DenseMatrix[Int] =
6  3
7  12

scala> m1 * m2
res1: breeze.linalg.DenseMatrix[Int] =
13  17
31  35

scala> val v1 = DenseMatrix.zeros[Int](2,3)
v1: breeze.linalg.DenseMatrix[Int] =
0  0  0
0  0  0

scala> m1(::, 0) := DenseVector(4,7)
res23: breeze.linalg.DenseVector[Int] = DenseVector(4, 7)

scala> m1
res24: breeze.linalg.DenseMatrix[Int] =
4  2
7  4

scala> m2(0, ::) := DenseVector(3,5).t
res25: breeze.linalg.Transpose[breeze.linalg.DenseVector[Int]] = Transpose(DenseVector(3, 5))

scala> m2
res26: breeze.linalg.DenseMatrix[Int] =
3  5
4  8

とりあえず行列計算試せたからここまで

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