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

[David Winsemius]

On Jul 27, 2011, at 5:53 PM, Paul Menzel wrote:

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

Right, but the fact that it _is_ described as a "generic" function  
will tell the clueful that other methods other than the default method  
may exist, and that their availability may vary with which packages  
are loaded.

>
> 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?

No. Read:

?par

It has both a value and a side-effect. Pay particular attention to its  
value for its first invocation. Then think about why its side-effect  
is what you want _after_ the loop. Then you may understand what is  
happening.  Report back to the class. (This isn't in the Introductory  
material you are reading?)

>
>
> Thanks,
>
> Paul

David Winsemius, MD
West Hartford, CT