sample.curves: Sample points on curves

In curveDepth: Tukey Curve Depth and Distance in the Space of Curves

Description

Samples points uniformly on curves interpolated as linear consequent segments.

Usage

sample.curves(curves, ptsPerCurve = as.integer(c(500)))

Arguments

curves	A list where each element is a function being a list containing a matrix coords (curves' values, d columns).
ptsPerCurve	A vector of numbers of points to be sampled on each curve. If length(ptsPerCurve) < length(curves) then the first entry of ptsPerCurve is considered only, and corresponds to the number of points on a curve.

Value

A list of curves with each entry being a list constiting of [[1]] the drawn curve being a matrix named coords, [[2]] length of the curve as in curves named length.init, and [[3]] length of the drawn curve named length.

References

Lafaye De Micheaux, P., Mozharovskyi, P. and Vimond, M. (2018). Depth for curve data and applications.

Examples

library(curveDepth)
# Load digits and transform them to curves
data("mnistShort017")
n <- 10 # cardinality of each class
m <- 50 # number of points to sample
cst <- 1/10 # a threshold constant
alp <- 1/8 # a threshold constant
curves0 <- images2curves(mnistShort017$`0`[, , 1:n])
curves1 <- images2curves(mnistShort017$`1`[, , 1:n])
set.seed(1)
curves0Smpl <- sample.curves(curves0, 2 * m)
curves1Smpl <- sample.curves(curves1, 2 * m)
# Calculate depths
depthSpace = matrix(NA, nrow = n * 2, ncol = 2)
depthSpace[, 1] = depth.curve.Tukey(
  c(curves0Smpl, curves1Smpl), curves0Smpl,
  exactEst = TRUE, minMassObj = cst/m^alp)
depthSpace[, 2] = depth.curve.Tukey(
  c(curves0Smpl, curves1Smpl), curves1Smpl,
  exactEst = TRUE, minMassObj = cst/m^alp)
# Draw the DD-plot
plot(NULL, xlim = c(0, 1), ylim = c(0, 1),
     xlab = paste("Depth w.r.t. '0'"),
     ylab = paste("Depth w.r.t. '1'"),
     main = paste("DD-plot for '0' vs '1'"))
grid()
# Draw the separating rule
dat1 <- data.frame(cbind(
  depthSpace, c(rep(0, n), rep(1, n))))
ddalpha1 <- ddalpha.train(X3 ~ X1 + X2, data = dat1,
                          depth = "ddplot",
                          separator = "alpha")
ddnormal <- ddalpha1$classifiers[[1]]$hyperplane[2:3]
pts <- matrix(c(0, 0, 1, ddnormal[1] / -ddnormal[2]),
              nrow = 2, byrow = TRUE)
lines(pts, lwd = 2)
# Draw the points
points(depthSpace[1:n, ],
       col = "red", lwd = 2, pch = 1)
points(depthSpace[(n + 1):(2 * n), ],
       col = "blue", lwd = 2, pch = 3)

Example output

Loading required package: Rcpp
Loading required package: ddalpha
Loading required package: MASS
Loading required package: class
Loading required package: robustbase
Loading required package: sfsmisc
Loading required package: geometry
Selected columns:  X3,   X1,   X2 

curveDepth documentation built on May 1, 2019, 8 p.m.