[rkward-devel] Problem with big objects

[Thomas Friedrichsmeier]

On Tuesday 09 October 2007, I. Soumpasis wrote:
> > > Example:
> > > pdf("plot.pdf")
> > > xyplot(bla bla bla)
> > > dev.off()
> > >
> > > does not produces plots, although my data exists.
> >
> > You mean this is, when you run inside local()? No idea on this problem.
>
> Yeap. The  same problem I have when I source the script file in R. If it
> helps.

Ok, I looked into this. The problem is that xyplot() does not actually print 
the plot automatically, but merely produces a plot object. When you run the 
statements one by one on the command line, the resulting object is 
auto-printed, causing it to be sent to the pdf() device.

However, if you lump the calls together then no auto-printing happens. This is 
not specific to local({}), but to anything that is evaluated in one go:
	{
		pdf("plot.pdf")
		xyplot(...)
		dev.off()
	}
does not work either, same as source(). Solution: call print() or plot() 
explicitely. E.g.:
	local ({
		pdf("plot.pdf")
		print (xyplot(...))
		dev.off()
	})
will work as expected.

> This <<- symbol means that it makes a local variable global?

Yes, it's exactly like "<-" except it always assigns in the globalenv().

> Is this local 
> function R's or rkward's function? I tried in R and it seems to work too.

Yes, it's an R base function. We just happen to use it a lot in RKWard.

> In RKWard it is really fast this way you are right. I will try to do it in
> my script. I just tried the example and it is really fast.

Another way (which is even better), is to put your code inside a function. 
This, too will avoid the many assignments in globalenv().

Regards
Thomas
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