On Wed, Jun 29, 2011 at 11:42 AM, Simon Goodman <s.j.good...@leeds.ac.uk> wrote:
> I have 2 related questions about functions.
>
> 1. I am writing a function to plot data from a time series with the form
>
> myplot<-function(data, d1,d2) { }
>
> Where d1 and d2 are two dates in a time series. The idea being that if no
> values for d1 and d2 are entered then the function defaults to plotting the
> whole time series, else it plots the data for the interval specified by d1
> and d2.
>
> I am attempting to test if the variable d1 has been inputted by using a
> different function, orginally posted on a R help forum by Brian Ripley.
>
> testObject <- function(object)
> {
> exists(as.character(substitute(object)))
> }
>
> here testObject(x) returns FALSE if x is not currently present a variable in
> the work space image.
>
> testObject works fine outside my plotting function, but not within it.... it
> always returns FALSE inside the plotting function even when d1 is being
> given by the user.
>
> I get the same result even if the testObject function is defined inside the
> plotting function....
>
> I suspect this may be due to enviroment being searched for d1.... but can't
> find work out how to make it search for d1 within the 'myplot' function - I
> think this can done using 'where' or 'environment' - but the documentation
> on these commands is a little opaque.
>
> 2. For the 'myplot' function I would also like to add a customlegend=TRUE
> (or FALSE) option, which determines if a custom legend is plotted (if not
> inputted it would default to TRUE), but haven't been able to find anything
> on how to specify this kind TRUE/FALSE of option for functions.
>
Try this:
We can just forward the first 1-3 arguments to window like this:
my.plot <- function(..., customlegend = TRUE) {
plot(window(...))
if (customlegend) legend("topleft", leg = "My custom legend")
}
tt <- ts(1:10)
# example 1
my.plot(tt, 3, 6)
# example 2
myplot(tt)
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