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rplotlatticetrellis

How to add new dots to existing lattice plot in R

I used the lattice package to draw a line plot.

library(lattice)  
xyplot(price~month,groups=perc,data=Edf,type='l',
       main="Percentile chart of OpRes Charge Rates Forcast", 
       ylab="OpRes Charge Rate ($/MWh)", xlab="Months",ylim=c(0,40),auto.key=TRUE)

Then I wanted to add some dots to the existing plot. 

points(rep(1,length(OpResWestJan)),OpResWestJan)

OpResWestJan is a vector, but the dots never appeared in the existing plot, and there were no warnings.

Solution

  • For the sake of completeness, here is a reproducible example. Simply store the created xyplot in a variable and then use update along with a custom panel function to add additional points. 

    library(lattice)

## create scatterplot
p <- xyplot(1:10 ~ 1:10)

## insert additional points
update(p, panel = function(...) {
  panel.xyplot(...)
  panel.xyplot(1:10, 10:1, pch = 4, col = "orange")
})

    scatterplot

    Alternatively, you can also create a second xyplot and use as.layer from latticeExtra to add it to your initial plot. 

    library(latticeExtra)

## create second scatterplot and add it to first plot
p2 <- xyplot(10:1 ~ 1:10, pch = 4, col = "orange")
p + as.layer(p2)

    Or, as suggested by @Pascal, use layer alongside with panel.points to achieve your goal.

    p + layer(panel.points(1:10, 10:1, pch = 4, col = "orange"))