igraph (version 1.0.0)

sample_sphere_surface: Sample vectors uniformly from the surface of a sphere

Description

Sample finite-dimensional vectors to use as latent position vectors in random dot product graphs

Usage

sample_sphere_surface(dim, n = 1, radius = 1, positive = TRUE)

Arguments

dim

Integer scalar, the dimension of the random vectors.

n

Integer scalar, the sample size.

radius

Numeric scalar, the radius of the sphere to sample.

positive

Logical scalar, whether to sample from the positive orthant of the sphere.

Value

• A dim (length of the alpha vector for sample_dirichlet) times n matrix, whose columns are the sample vectors.

Details

sample_sphere_surface generates uniform samples from $S^{dim-1}$ (the (dim-1)-sphere) with radius radius, i.e. the Euclidean norm of the samples equal radius.

See Also

Other latent position vector samplers: sample_dirichlet; sample_sphere_volume

Examples

lpvs.sph    <- sample_sphere_surface(dim=10, n=20, radius=1)
RDP.graph.3 <- sample_dot_product(lpvs.sph)
vec.norm    <- apply(lpvs.sph, 2, function(x) { sum(x^2) })
vec.norm