# sample_sphere_surface

From igraph v1.0.0
by Gabor Csardi

##### Sample vectors uniformly from the surface of a sphere

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
```

*Documentation reproduced from package igraph, version 1.0.0, License: GPL (>= 2)*

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