[R] time (or output of function) in the R prompt

[Liaw, Andy]

> On Thu, 11 Apr 2002, Liaw, Andy wrote:
> 
> > Dear R-help,
> >
> > Would it be possible to have the "prompt" option accept a 
> function, such as
> > date()?  This way, I can easily deduce the elapse time of 
> top level R
> > expressions.  This would be similar to how Unix shells 
> handle their prompt
> > variables.
> 
> You can almost do this with the taskCallback Manager
> 
> > h <- taskCallbackManager()
> > h$add(function(expr, value, ok, visible) {
> 		options(prompt=paste(date(),"> "));
> 		return(TRUE)},
>        name="dateprompt")
> 
> Thu Apr 11 10:47:06 2002 > 1+1
> [1] 2
> Thu Apr 11 10:48:28 2002 >
> 
> I say `almost' because the time is updated only when you 
> actually compute
> something.  If you just press <return> it doesn't change. 
> Apart from that
> it works.

Thanks a lot Thomas!  This gives the same desired effect, thru different
mechanism (than the Unix shells?).  I can also use it to add the output of
getwd() to remind myself which R session I'm staring at, when I have several
running simultaneously.

Also thanks to DTL for providing taskCallbackManager().  It's a lot more
useful than my original question about timed autosave.

Cheers,
Andy


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