[R] plotting on a reverse log scale

[Duncan Murdoch]

On 7/6/2005 3:36 PM, Michael Friendly wrote:
> I'd like to do some plots of historical event data on a reverse log 
> scale, started, say at the year 2000 and going
> backwards in time, with tick marks spaced according to log(2000-year).  
> For example, see:
> 
> http://euclid.psych.yorku.ca/SCS/Gallery/images/log-timeline.gif
> 
> As an example, I'd like to create a density plot of such data with the 
> horizontal axis reverse-logged,
> a transformation of this image:
> http://euclid.psych.yorku.ca/SCS/Gallery/milestone/Test/mileyears1.gif
> 
> Some initial code to do a standard density plot looks like this:
> 
> mileyears <- read.csv("mileyears3.csv", skip=1, 
> col.names=c("key","year","where","add","junk"))
> mileyears <- mileyears[,2:4]
> 
> years <- mileyears$year
> years1500 <- years[years>1500]
> dens <- density(years1500, from=1500, to=1990)
> plot(dens)
> rug(years1500)
> 
> I could calculate log(2000-year), but I'm not sure how to do the 
> plotting, do some minor tick marks
> and label the major ones, say at 100 year intervals.

I think you'll have to do everything explicitly.  That is, something 
like this:

years1500 <- runif(500, 1500, 1990)  # some fake data
x <- log(2000-years1500)
from <- log(2000-1990)
to <- log(2000-1500)
plot(density(x, from=from, to=to), axes=F)
rug(x)

labels <- pretty(years1500)
labels <- labels[labels<2000]
axis(1, labels, at=log(2000-labels))

minorticks <- pretty(years1500, n=20)
minorticks <- minorticks[minorticks<2000]
axis(1, labels=FALSE, at=log(2000-minorticks), tcl=-0.25)

axis(2)
box()

Duncan Murdoch