project_to_curve: Project a set of points to the closest point on a curve

In princurve: Fit a Principal Curve in Arbitrary Dimension

Description

Finds the projection index for a matrix of points x, when projected onto a curve s. The curve need not be of the same length as the number of points.

Usage

project_to_curve(x, s, stretch = 2)

Arguments

x	a matrix of data points.
s	a parametrized curve, represented by a polygon.
stretch	A stretch factor for the endpoints of the curve, allowing the curve to grow to avoid bunching at the end. Must be a numeric value between 0 and 2.

Value

A structure is returned which represents a fitted curve. It has components

s	The fitted points on the curve corresponding to each point x
ord	the order of the fitted points
lambda	The projection index for each point
dist	The total squared distance from the curve
dist_ind	The squared distances from the curve to each of the respective points

See Also

principal_curve

Examples

t <- runif(100, -1, 1)
x <- cbind(t, t ^ 2) + rnorm(200, sd = 0.05)
s <- matrix(c(-1, 0, 1, 1, 0, 1), ncol = 2)

proj <- project_to_curve(x, s)

plot(x)
lines(s)
segments(x[, 1], x[, 2], proj$s[, 1], proj$s[, 2])

Example output

princurve documentation built on Jan. 18, 2021, 5:06 p.m.