tsxpos {plotrix} | R Documentation |
Calculate equispaced x positions.
Description
Calculate equispaced x positions of values that have been plotted with the plot command.
Usage
tsxpos(x,xlim,nint)
Arguments
x |
A vector of numeric values or a time series object created with the ts function. |
xlim |
Explicit x limits for the x positions. |
nint |
The number of intervals between x positions. |
Details
‘tsxpos’ calculates equispaced x positions for a vector of values or a time series created with the ‘ts’ command from the stats package. It assumes that the default x limits have been used in the existing plot. It adds the appropriate padding if ‘par("xaxs")’ is "r". It is mainly useful when x axis labels or some other markers are to be added to a time series plot.
A plot device must be open. If the user wishes to specify explicit x limits or the number of intervals (not values), these will override the calculations from the x values.
Value
The calculated x positions in user units.
Author(s)
Jim Lemon (thanks to Prof J.C. Nash for the idea)
Examples
# create a vector of numbers
y<-rnorm(28)
par(mfrow=c(2,1),mar=c(6,4,4,2))
plot(y,main="Plot of the values")
# convert it into a time series object
yt<-ts(y,start=2011,frequency=12)
# don't use the default axis
plot(yt,main="Plot of the time series",xaxt="n",xlab="Month")
labelpos<-tsxpos(yt)
# display an axis showing the months only
staxlab(1,labelpos,rep(month.abb,length.out=28))
par(mfrow=c(1,1),mar=c(5,4,4,2))