Hi I am tying to use the apache commons math lib to solve systems of linear equations. To this end I...

# getting-started

[Thomas Dost]

Hi I am tying to use the apache commons math lib to solve systems of linear equations. To this end I have this code

var t: Array<Array<Double>> = arrayOf(
        arrayOf(1.0,2.0),
        arrayOf(1.0,2.0),
       arrayOf(1.0,2.0))
        
var n: RealMatrix = MatrixUtils.createRealMatrix(t)

but I get following error

e: file:///home/td/NLO3/src/main/kotlin/Function.kt:210:58 Type mismatch: inferred type is Array<Array<Double>> but Array<(out) DoubleArray!>! was expected

changing t's type to Array<(out) DoubleArray!>! did not help. Does anyone have an idea how to fix that. If there is an easier solution e.g. maybe an mathlib in Kotlin I am also interested in that

Thank you very much for your time

[Joffrey]

When you use the generic arrayOf function, it gives you a generic Array<Double>. What you want is to use doubleArrayOf() so you get a DoubleArray (which is different, because it's an array of primitives instead of an array of Double object wrappers):

var t = arrayOf(
    doubleArrayOf(1.0,2.0),
    doubleArrayOf(1.0,2.0),
    doubleArrayOf(1.0,2.0),
)

[Thomas Dost]

That was fast. Thank you very much