thigmophobe.labels: Place labels away from the nearest point

Description

thigmophobe.labels places labels adjacent to each point, offsetting each label in the direction returned by thigmophobe.

Usage

thigmophobe.labels(x,y,labels=NULL,text.pos=NULL,...)

Arguments

x,y

Numeric data vectors or a list with two components. Typically the x/y coordinates of plotted points.

labels

A vector of strings that will be placed adjacent to each point. Defaults to the indices of the coordinates.

text.pos

An optional vector of text positions (see text).

...

additional arguments are passed to text

Value

A vector of directions away from the point nearest to each point.

Details

Typically used to automatically place labels on a scatterplot or similar to avoid overlapping labels. thigmophobe.labels will sometimes place a label off the plot or fail to separate labels in clusters of points. The user can manually adjust the errant labels by running thigmophobe first and saving the returned vector. Then modify the position values to place the labels properly and pass the edited vector to thigmophobe.labels as the text.pos argument. This takes precedence over the positions calculated by thigmophobe.

thigmophobe will fail with only two labels, as it can't figure out the nearest neighbors. If you really want to use this with two labels, just eyeball the plot and work out in which direction the labels will go. Then pass the directions to thigmophobe.labels as the text.pos argument. When all else fails, look to sampplaceLabels.

Both pointLabel in the maptools package and spread.labs in the TeachingDemos package use more sophisticated algorithms to place the labels and are worth a try if thigmophobe just won't get it right.

Examples

Run this code

# NOT RUN {
 x<-rnorm(20)
 y<-rnorm(20)
 xlim<-range(x)
 xspace<-(xlim[2]-xlim[1])/20
 xlim<-c(xlim[1]-xspace,xlim[2]+xspace)
 ylim<-range(y)
 yspace<-(ylim[2]-ylim[1])/20
 ylim<-c(ylim[1]-yspace,ylim[2]+yspace)
 plotlabels<-
  c("one","two","three","four","five","six","seven","eight","nine","ten",
  "eleven","twelve","thirteen","fourteen","fifteen","sixteen","seventeen",
  "eighteen","nineteen","twenty")
 plot(x=x,y=y,xlim=xlim,ylim=ylim,main="Test thigmophobe.labels")
 # skip the almost invisible yellow label, make them bold
 thigmophobe.labels(x,y,plotlabels,col=c(2:6,8:12),font=2)
# }