Plot two size vector length with xyplot

Question

Please note that this is a simplified version (and therefore duplicate of my earlier post):

https://stackoverflow.com/questions/18358694/xyplot-2-separate-data-frame-lengths

It may well be that it contained too much information, however quite basic was asked.

So here again:

I would like to plot 2 columns of different length with xyplot (only xyplot please).

The data:

Data <- data.frame(var1=rnorm(10,0,1),prob=seq(0.023,0.365,length=10))
Long <- data.frame(var2=rnorm(20,2,3))

How I would plot the Long (var2) vector of length 20 onto the plot of "Data" where (prob~var1) is plotted first.

Answer 1

You can use approx() inside your call to xyplot to interpolate the values of Data$prob after passing Long$var2 as a separate variable in the call. Notice the custom prepanel plot to adjust the limits.

lattice::xyplot(prob ~ var1, data = Data, z = Long$var2,
                xlab = "Var1, Var2",
                prepanel = function(x, y, z, ...) {
                  list(xlim = range(x, z),
                       ylim = range(y))
                },
                panel = function(x, y, z, ...) {
                  b <- approx(y, n = length(z))$y
                  panel.xyplot(x, y, ...)
                  panel.xyplot(z, b, col = "orange", ...)
                })

EDIT: Actually, it is much cleaner to just reshape the data first.

dd <- rbind(data.frame(var = "var1",
                       val = Data$var1,
                       prob = Data$prob),
            data.frame(var = "var2",
                       val = Long$var2,
                       prob = approx(Data$prob, n = 20)$y))

xyplot(prob ~ val, data = dd, groups = var, auto.key = TRUE)