[R] Putting splom in a function

[Deepayan Sarkar]

On 2/14/07, Roberto Perdisci <roberto.perdisci at gmail.com> wrote:
> Hello R list,
>   I have a little problem with splom. I'd like to wrap it in a
> function, for example:
>
> multi.scatterplot <- function(data,groups,cols,colors) {
>     splom(~data[,cols], groups = as.symbol(groups), data = data, panel
> = panel.superpose, col=colors)
> }
>
> and then call it like in
>
> multi.scatterplot(iris,"Species",1:4,c("green","blue","red"))
>
> but the problem is:
> Error in form$groups[form$subscr] : object is not subsettable

Non-standard evaluation is a pain generally. See, e.g.,
lattice:::stripplot.formula for a possible solution that seems to
work.

> if I use
>               groups = groups
> instead of
>               groups = as.symbol(groups)
>
> shomthing is plotted, but not the correct scatterplot.

Try groups = eval(as.name(groups))

Deepayan

> I think the problem is that I don't cast the 'groups' variable to the
> correct type. Besides as.symbol() I tried also as.expression(),
> because ?xyplot says "groups: a variable or expression to be evaluated
> in the data frame specified by 'data'".
> What is the correct type? What as.* should I use?
>
> thank you,
> regards,
> Roberto
>
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