// chooseCentroids picks random centroids based on the min and max values in the matrix
// and return a k by m matrix of the centroids.
func (c randCentroids) ChooseCentroids(mat *matrix.DenseMatrix, k int) *matrix.DenseMatrix {
_, cols := mat.GetSize()
centroids := matrix.Zeros(k, cols)
for colnum := 0; colnum < cols; colnum++ {
r := mat.ColSlice(colnum)
minj := float64(0)
// min value from column
for _, val := range r {
minj = math.Min(minj, val)
}
// max value from column
maxj := float64(0)
for _, val := range r {
maxj = math.Max(maxj, val)
}
// create a slice of random centroids
// based on maxj + minJ * random num to stay in range
for h := 0; h < k; h++ {
randInRange := ((maxj - minj) * rand.Float64()) + minj
centroids.Set(h, colnum, randInRange)
}
}
return centroids
}