How to add a single new contour to a contour plot in Lattice

Question

I have produced a filled contourplot using contourplot function in the Lattice package. I would like to be able to emphasise one of the contour lines produced by this function, e.g. by changing lwd=2, and de-emphasise the other contour lines produced, e.g. by setting changing the remaining contour line colours to grey.

For example, I would like the equivalent of adding

contourplot(
Male ~ Year * Age, 
data=this.ds, region=F, labels=F, lwd=2, at=c(0, 0.01, 1))

To

contourplot(
Male ~ Year * Age, 
data=this.ds, 
region=T, col.regions=rev(heat.colors(200)), 
cuts=50, main="", sep="")

I recognise that the answer is likely to involve the functions update, panel, and/or layer (if using latticeExtra), but I my understanding of the underlying logic/structure of lattice objects is not good enough to figure out what to do.

Edit

Thanks for your help. I basically used the first answer, but with the following slight modification to be able to point out a couple of features on the contour line:

require(lattice)
require(latticeExtra)

Part1 <- contourplot(Female ~ Year * Age, 
                     data=this.ds,
                     region=T, 
                     col.regions=rev(heat.colors(200)),
                     cuts=50, 
                     main="", 
                     labels=F,
                     col="grey",
                     sep="")

Part2 <- contourplot(Female ~ Year * Age,
                     data=this.ds,
                     region=F,
                     labels=F,
                     lwd=2,
                     at=c(0, 0.01, 1),
                     panel=function(...){
                     panel.contourplot(...)
                      panel.segments(x0=c(1840, 1900, 2000, 1840), 
                                     x1=c(1900, 1900, 2000, 2000), 
                                     y0=c(40.5, 0, 0, 64), 
                                     y1=c(40.5, 40.5, 64, 64), 
                                     lty="dashed")
                     }                    
)


Plot.Final <- Part1+ Part2 

print(Plot.Final)

Please share some code with us so we can use it to help you (reproducible example: http://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example) — statquant, Aug 22 '13 at 12:54

John Paul · Accepted Answer · 2013-08-22T13:51:57.277

2

Load the latticeExtra library. Then:

Part1<-contourplot(
    Male ~ Year * Age, 
    data=this.ds, 
    region=T, col.regions=rev(heat.colors(200)), 
    cuts=50, main="", sep="")

Part2<-contourplot(
    Male ~ Year * Age, 
    data=this.ds, region=F, labels=F, lwd=2, at=c(0, 0.01, 1))

Plot.Final<-Part1+Part2

That should combine the graphs as you wish. If needed you may need to set xlim, ylim and labels so that everything looks OK.

edited Aug 22 '13 at 13:51

answered Aug 22 '13 at 13:41

John Paul

12,196
6
55
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That's great. Thanks. So latticeExtra makes lattice a lot more ggplot-like in terms of how plots are specified? – JonMinton Aug 22 '13 at 13:50
I have never used ggplot- so hopefully someone else can answer this. – John Paul Aug 22 '13 at 13:53

score 0 · Answer 2 · answered Aug 22 '13 at 14:07

0

Use contour instead of contourplot.

bar<-matrix(runif(100,nrow=10))
contour(bar)
contour(bar,levels = 0.2, lwd=3, add=TRUE)

Edit: turns out you don't even need to do that. Unlike contourplot, contour allows yo uto specify a vector of line widths (or colors, or whatever), so contour(bar,lwd=c(2,1,1,1,1,)) will suffice.

Edit 2: My apologies: this is in the graphics package.

answered Aug 22 '13 at 14:07

Carl Witthoft

20,573
9
43
73

Thanks. I've already got too much of my code using lattice to able to start from scratch, unfortunately. – JonMinton Aug 22 '13 at 14:19

How to add a single new contour to a contour plot in Lattice

Edit

2 Answers2