R igraph manual pages

sample_sphere_surface {igraph}

R Documentation

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.

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.

Value

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

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

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