interpPlot: Plot an Interpolation Between Two Related Data Sets

In heplots: Visualizing Hypothesis Tests in Multivariate Linear Models

Plot an Interpolation Between Two Related Data Sets

Description

Plot an interpolation between two related data sets, typically transformations of each other. This function is designed to be used in animations.

Usage

interpPlot(
  xy1,
  xy2,
  alpha,
  xlim,
  ylim,
  points = TRUE,
  add = FALSE,
  col = palette()[1],
  ellipse = FALSE,
  ellipse.args = NULL,
  abline = FALSE,
  col.lines = palette()[2],
  lwd = 2,
  id.method = "mahal",
  labels = rownames(xy1),
  id.n = 0,
  id.cex = 1,
  id.col = palette()[1],
  segments = FALSE,
  segment.col = "darkgray",
  ...
)

Arguments

xy1	First data set, a 2-column matrix or data.frame
xy2	Second data set, a 2-column matrix or data.frame
alpha	The value of the interpolation fraction, typically (but not necessarily) 0 <= alpha <= 1).
xlim, ylim	x, y limits for the plot. If not specified, the function uses the ranges of rbind(xy1, xy2).
points	Logical. Whether to plot the points in the current interpolation?
add	Logical. Whether to add to an existing plot?
col	Color for plotted points.
ellipse	logical. TRUE to plot a dataEllipse
ellipse.args	other arguments passed to dataEllipse
abline	logical. TRUE to plot the linear regression line for XY
col.lines	line color
lwd	line width
id.method	How points are to be identified. See showLabels.
labels	observation labels
id.n	Number of points to be identified. If set to zero, no points are identified.
id.cex	Controls the size of the plotted labels. The default is 1
id.col	Controls the color of the plotted labels.
segments	logical. TRUE to draw lines segments from xy1 to xy
segment.col	line color for segments
...	other arguments passed to plot()

Details

Points are plotted via the linear interpolation,

XY = XY1 + \alpha (XY2 - XY1)

The function allows plotting of the data ellipse, the linear regression line, and line segments showing the movement of points.

Interpolations other than linear can be obtained by using a non-linear series of alpha values. For example alpha=sin(seq(0,1,.1)/sin(1) will give a sinusoid interpolation.

Value

Returns invisibly the interpolated XY points.

Note

The examples here just use on-screen animations to the console graphics window. The animation package provides facilities to save these in various formats.

Author(s)

Michael Friendly

See Also

dataEllipse, showLabels, animation

Examples

#################################################
# animate an AV plot from marginal to conditional
#################################################
data(Duncan, package="carData")
duncmod <- lm(prestige ~ income + education, data=Duncan)
mod.mat <- model.matrix(duncmod)

# function to do an animation for one variable
dunc.anim <- function(variable, other, alpha=seq(0, 1, .1)) {
  var <- which(variable==colnames(mod.mat))
  duncdev <- scale(Duncan[,c(variable, "prestige")], scale=FALSE)
  duncav <- lsfit(mod.mat[, -var], cbind(mod.mat[, var], Duncan$prestige), 
          intercept = FALSE)$residuals
  colnames(duncav) <- c(variable, "prestige")
  
  lims <- apply(rbind(duncdev, duncav),2,range)
  
  for (alp in alpha) {
    main <- if(alp==0) paste("Marginal plot:", variable)
      else paste(round(100*alp), "% Added-variable plot:", variable)
    interpPlot(duncdev, duncav, alp, xlim=lims[,1], ylim=lims[,2], pch=16,
      main = main,
      xlab = paste(variable, "| ", alp, other),
      ylab = paste("prestige | ", alp, other),
      ellipse=TRUE, ellipse.args=(list(levels=0.68, fill=TRUE, fill.alpha=alp/2)), 
      abline=TRUE, id.n=3, id.cex=1.2, cex.lab=1.25)
    Sys.sleep(1)
  }
}

# show these in the R console
if(interactive()) {
dunc.anim("income", "education")

dunc.anim("education", "income")
}

############################################
# correlated bivariate data with 2 outliers
# show rotation from data space to PCA space
############################################

set.seed(123345)
x <- c(rnorm(100), 2, -2)
y <- c(x[1:100] + rnorm(100), -2, 2)
XY <- cbind(x=x, y=y)
rownames(XY) <- seq_along(x)
XY <- scale(XY, center=TRUE, scale=FALSE)

# start, end plots

car::dataEllipse(XY, pch=16, levels=0.68, id.n=2)
mod <- lm(y~x, data=as.data.frame(XY))
abline(mod, col="red", lwd=2)

pca <- princomp(XY, cor=TRUE)
scores <- pca$scores
car::dataEllipse(scores, pch=16, levels=0.68, id.n=2)
abline(lm(Comp.2 ~ Comp.1, data=as.data.frame(scores)), lwd=2, col="red")

# show interpolation

# functions for labels, as a function of alpha
main <- function(alpha) {if(alpha==0) "Original data" 
  else if(alpha==1) "PCA scores"
  else paste(round(100*alpha,1), "% interpolation")}
xlab <- function(alpha) {if(alpha==0) "X"
  else if(alpha==1) "PCA.1"
  else paste("X +", alpha, "(X - PCA.1)")}
ylab <- function(alpha) {if(alpha==0) "Y"
  else if(alpha==1) "PCA.2"
  else paste("Y +", alpha, "(Y - PCA.2)")}

interpPCA <- function(XY, alpha = seq(0,1,.1)) {
  XY <- scale(XY, center=TRUE, scale=FALSE)
  if (is.null(rownames(XY))) rownames(XY) <- 1:nrow(XY)
  pca <- princomp(XY, cor=TRUE)
  scores <- pca$scores

  for (alp in alpha) {
    interpPlot(XY, scores, alp, 
      pch=16,
      main = main(alp),
      xlab = xlab(alp),
      ylab = ylab(alp),
      ellipse=TRUE, ellipse.args=(list(levels=0.68, fill=TRUE, fill.alpha=(1-alp)/2)), 
      abline=TRUE, id.n=2, id.cex=1.2, cex.lab=1.25, segments=TRUE)
    Sys.sleep(1)
  }
}

# show in R console
if(interactive()) {
interpPCA(XY)
}

## Not run: 
library(animation)
saveGIF({
  interpPCA(XY, alpha <- seq(0,1,.1))},
  movie.name="outlier-demo.gif", ani.width=480, ani.height=480, interval=1.5)


## End(Not run)

heplots documentation built on May 29, 2024, 9:24 a.m.