[R] Lattice xyplot with two y axis

[Richard.Cotton at hsl.gov.uk]

> I have some data which needs to be plotted with lattice.
> 
> library(lattice)
> cars <- c(0.1, 0.3, 0.6, 0.4, 0.9)
> trucks <- c(0.2, 0.5, 0.4, 0.5, 0.1)
> drivers<-c(121,145,167,200, 210)
> year<-c(2005,2006,2007,2008,2009)
> type<-c("local","local","foreign","foreign","foreign")
> xyplot(cars+trucks~year|type, data=df3, type="o")
> 
> Basically, I need to show "drivers" as well on a secondary y-axis. Is 
this
> possible with lattice and xyplot?

The trick is to use a custom y-scale component to draw the second axis. 
You also need to manually make space between panels using the between 
argument.

#Your data, as before
library(lattice)
cars <- c(0.1, 0.3, 0.6, 0.4, 0.9)
trucks <- c(0.2, 0.5, 0.4, 0.5, 0.1)
drivers<-c(121,145,167,200, 210)
year<-c(2005,2006,2007,2008,2009)
type<-c("local","local","foreign","foreign","foreign")

#Custom y-scale component
myyscale.component <- function(...)
{
  ans <- yscale.components.default(...)
  ans$right <- ans$left
  foo <- ans$right$labels$at
  ans$right$labels$labels <- as.character(200*foo)          #200 is the 
scale factor difference between axes, adjust as necessary
  ans
} 

#The plot
xyplot(cars+trucks+drivers/200~year|type, 
   type="o",
   scales=list(
      x=list(alternating=FALSE), 
      y=list(relation="free", rot=0)),      # relation="free" separates 
the panels
   yscale.component=myyscale.component,
   between=list(x=2),                       #between creates more space 
between the panels - you may need to adjust this value
   par.settings=list(layout.widths=list(right.padding=6)), #this creates 
more space on the right hand side of the plot
   ylab=NULL, 
   key=simpleKey(text=c("cars", "trucks", "drivers"))) 


Regards,
Richie.

Mathematical Sciences Unit
HSL



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