plot.two: plot.two
In finite2/peter.utilities: Peter's utility functions

Allows two variables on different scales to be plotted on one set of axes. The scales are added on the left and right sides of the graph with specified labels.

plot.two(x1, y1, x2, y2, xlim = NULL, ylim1 = NULL, ylim2 = NULL, 
    type1 = "points", type2 = "points", col1 = "red", col2 = "blue", 
    cex = 1.5, pch1 = 16, pch2 = 16, xlab = "", ylab1 = "", ylab2 = "", 
    add = FALSE, xpos = 1)

`x1,y1,x2,y2`	Data to be plotted
`xlim,ylim1,ylim2`	Optional limits for the 3 axes. If not specified the default limits are used (see `pretty`)
`type1,type2`	This should either be points (default) or connected. The latter joins up the points.
`col1,col2`	Colours of each data type to be plotted
`xlab,ylab1,ylab2`	Axis labels
`add`	Allows plotting to preconstructed set of axes. This may be of use if using `split.screen` to generate multiple graphs on a single screen or figure