[R] ?plot: Add an example on how to plot functions to the help of `plot`.

[Paul Menzel]

Am Mittwoch, den 27.07.2011, 17:21 -0400 schrieb David Winsemius:
> On Jul 27, 2011, at 4:53 PM, Paul Menzel wrote:

> > Am Mittwoch, den 27.07.2011, 13:26 -0700 schrieb Bert Gunter:
> >> Paul:
> >> No such change is needed.
> >
> > Well the fact is, that I as a beginner was looking for who I could  
> > plot normal functions, so one more example would have helped me.
> >
> >> You do not understand S3 methods.
> >
> > That is probably true.
> >
> >> See ?plot.default and read about S3 methods (e.g. in the tutorial
> >> Introduction to R or the Language manual).
> >
> > Searching for »s3 m« in [1] did not give me a good explanation. I have
> > not yet read the language manual.
> >
> > By trial and error I still suggest to add the following.
> >
> >        # Plot the graph of a function f(x) = x^3 with the points  
> > connected by lines.
> >        # If you want to plot the graph as a curve please look into  
> > `curve()`.
> >        y <- seq(1:5)
> >        plot(y, y**3, type="l")
> >
> > This would have helped me as a beginner.
> 
> I think that what Bert might have been trying to get you to do was to  
> type:
> 
> ?plot.function  # which is what you might once you do get a better  
> understanding S3 methods.

Thank you. So S3 methods seem to be a wrapper for another method. Well I
have to read up about that.

So my newest suggestion is to add a comment to

	plot(sin, -pi, 2*pi)

in `?plot`. Like

	plot(sin, -pi, 2*pi) # Cf. ?plot.function

as `plot.function` is not explicitly mentioned in `?plot`.

One further comment regarding the examples in `?plot.function`. Trying
those in order

        op <- par(mfrow = c(2, 2))
        chippy <- function(x) sin(cos(x)*exp(-x/2))
        plot (chippy, -8, -5)
        for(ll in c("", "x", "y", "xy"))
        curve(log(1+x), 1, 100, log = ll,
              sub = paste("log= '", ll, "'", sep = ""))
        par(op)

I do not see any effect executing `par(op)` at the end. Reading `?par` I
assume it should go before the for loop?


Thanks,

Paul
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