[R] How to stamp my graphs with date and time

[Deepayan Sarkar]

On Wed, Apr 21, 2010 at 4:02 PM, David Winsemius <dwinsemius at comcast.net> wrote:
>
> On Apr 21, 2010, at 6:58 PM, David Winsemius wrote:
>
>> Sarkar offers a worked example of taking user input regarding location for
>> locating a grid viewport outside the plot area.
>>
>> http://lmdvr.r-forge.r-project.org/figures/figures.html
>>
>> See Figure 12.1
>>
>> state <- data.frame(state.x77, state.region)
>> trellis.vpname("xlab", prefix = "plot1")
>> trellis.vpname("strip", column = 2, row = 2, prefix = "plot2")
>>
>>
>> data(Chem97, package = "mlmRev")
>> qqmath(~ gcsescore | factor(score), Chem97, groups = gender,
>>      f.value = function(n) ppoints(100),
>>      aspect = "xy",
>>      page = function(n) {
>>          cat("Click on plot to place legend", fill = TRUE)
>>          ll <- grid.locator(unit = "npc")
>>          if (!is.null(ll))
>>              draw.key(simpleKey(levels(factor(Chem97$gender))),
>>                       vp = viewport(x = ll$x, y = ll$y),
>>                       draw = TRUE)
>>      })
>>
>
> Furthermore when I try:
>
> mtext(date(), side=3, line=4, adj=0)
>
> .... I get a datetime stamp even though I am mixing graphic paradigms. This
> would seem to be one of those instances where you needn't worry about
> getting the internal coordinates to match up.

Appearances can be deceiving. Try to create a PDF file with this, and
you will get

> pdf()
> xyplot(1 ~ 1)
> mtext(date(), side=1, line=4, adj=0)
Error in mtext(date(), side = 1, line = 4, adj = 0) :
  plot.new has not been called yet
> dev.off()

Try to copy the screen device to PDF, and you will get

> dev.copy(pdf, file = "/tmp/foo.pdf")
Error in dev.copy(pdf, file = "/tmp/foo.pdf") : invalid graphics state

For a footnote in lattice plots, page is the appropriate argument to
use. Adapting an example from the book (section 9.3), the following
will add a timestamp to all subsequent lattice plots:

lattice.options(default.args = list(page = function(n) {
    panel.text(lab = sprintf("%s", date()), x = 0.99, y = 0.05, adj = 1)
}))

xyplot(1 ~ 1)


-Deepayan