Exemplo n.º 1
0
// NewNormal creates a new Normal with the given mean and covariance matrix.
// NewNormal panics if len(mu) == 0, or if len(mu) != sigma.N. If the covariance
// matrix is not positive-definite, the returned boolean is false.
func NewNormal(mu []float64, sigma mat64.Symmetric, src *rand.Rand) (*Normal, bool) {
	if len(mu) == 0 {
		panic(badZeroDimension)
	}
	dim := sigma.Symmetric()
	if dim != len(mu) {
		panic(badSizeMismatch)
	}
	n := &Normal{
		src:   src,
		dim:   dim,
		mu:    make([]float64, dim),
		sigma: mat64.NewSymDense(dim, nil),
		chol:  mat64.NewTriDense(dim, true, nil),
	}
	copy(n.mu, mu)
	n.sigma.CopySym(sigma)
	// TODO(btracey): Change this to the input Sigma, in case it is diagonal or
	// banded.
	ok := n.chol.Cholesky(n.sigma, true)
	if !ok {
		return nil, false
	}
	for i := 0; i < dim; i++ {
		n.logSqrtDet += math.Log(n.chol.At(i, i))
	}
	return n, true
}
func cholesky(order int, elements []float64) fmt.Formatter {
	t := mat64.NewTriDense(order, false, nil)
	t.Cholesky(mat64.NewSymDense(order, elements), false)
	return mat64.Formatted(t)
}
Exemplo n.º 3
0
func resizeTriDense(m *mat64.TriDense, dim int) *mat64.TriDense {
	if m == nil || cap(m.RawTriangular().Data) < dim*dim {
		return mat64.NewTriDense(dim, true, nil)
	}
	return mat64.NewTriDense(dim, true, m.RawTriangular().Data[:dim*dim])
}