[Rd] example(..., ask=getOption("example.ask"))

Henrik Bengtsson hb at stat.berkeley.edu
Wed Sep 13 11:51:51 CEST 2006


I wish to return to the topic "[Rd] example(ask = .) - default ?"
discussed in R-devel on May 1, 2006, because I think it is related to
my problem.

In one of my Rd examples I generate multiple (20-30!) PNG files using
png()/dev.off().  I noticed that I get a "Hit <Return> to see next
plot:" for each png() call, when calling example() [interactively].

The code for example() has:

    if (ask == "default")
        ask <- echo && dev.interactive(orNone = TRUE)
    if (ask) {
        if (.Device != "null device") {
            opar <- par(ask = TRUE)
        op <- options(par.ask.default = TRUE)
        on.exit(options(op), add = TRUE)

When calling example() interactively, either with ask=TRUE (explicitly
or indirectly with getOption("example.ask") == "default"), option
'par.ask.default' is set to TRUE.  This seems to be the reason for the
above.  Example:

> options(par.ask.default=TRUE)
> png("foo.png"); plot(1); dev.off()
Hit <Return> to see next plot:
null device
> options(par.ask.default=FALSE)
> png("foo.png"); plot(1); dev.off()
null device



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