Kotlin Extension function to find index of minimum value of given row of 2D array

minIndexOfColumnsOfRow.kt

fun Array<DoubleArray>.minIndexOfColumnsOfRow(rowNumber: Int): Int {
    var minNum = this[0][rowNumber]
    var minIndex = 0
    repeat(this.size)
    { x ->
        if (minNum > this[x][rowNumber]) {
            minIndex = x
            minNum = this[x][rowNumber]
        }
    }
    return minIndex
}