tdaunif (version 0.2.0)

triangles: Sample (with noise) from planar triangles

Description

This function generates uniform and stratified samples from configurations of planar triangles in 2-dimensional space, optionally with noise.

Usage

sample_triangle_planar(n, triangle, bins = 1, sd = 0)

Arguments

n

Number of observations.

triangle

The (x,y) coordinates of the vertices of a triangle, formatted in a 2x3 matrix

bins

Number of intervals per dimension to stratify by. Default set to 1, which generates a uniform sample.

sd

Standard deviation of (independent multivariate) Gaussian noise.

Details

The sample is generated by an area-preserving parameterization of the planar triangle. This parameterization was derived through the method for sampling 2-manifolds as described by Arvo (2001).

References

J Arvo (2001) Stratified Sampling of 2-Manifolds. SIGRAPH 2001 (State of the Art in Monte Carlo Ray Tracing for Realistic Image Synthesis), Course Notes, Vol. 29. https://www.cs.princeton.edu/courses/archive/fall04/cos526/papers/course29sig01.pdf

Examples

set.seed(23004L)

#Uniformly sampled equilateral planar triangle in 2-space
equilateral_triangle <- cbind(c(0,0), c(0.5,sqrt(3)/2), c(1,0))
x <-  sample_triangle_planar(10000, equilateral_triangle)
plot(x, asp = 1, pch = 19, cex = .25)

#Stratified sample of equilateral planar triangle in 2-space with 100 bins
equilateral_triangle <- cbind(c(0,0), c(0.5,sqrt(3)/2), c(1,0))
x <-  sample_triangle_planar(10000, equilateral_triangle, bins = 100)
plot(x, asp = 1, pch = 19, cex = .25)

#Uniformly sampled equilateral planar triangle in 2-space with Gaussian noise
equilateral_triangle <- cbind(c(0,0), c(0.5,sqrt(3)/2), c(1,0))
x <-  sample_triangle_planar(10000, equilateral_triangle, sd = .1)
plot(x, asp = 1, pch = 19, cex = .25)