[datatable-help] ggplot2 and data.table

[Timothée Carayol]

You are right -- I should have given a bit more context.

1) The usual ggplot2 syntax mostly works with data.tables, though sometimes
coercing to a data.frame is necessary. I do not have a reproducible example
of that at hand, but I thought it's probably something that would require a
fix in ggplot2, and not data.table. I'll try to find you a reproducible
example if that's useful.

2) What I wanted to allow, was to call ggplot inside a data.table call,
e.g.

test <- data.table(
                   a=rnorm(4*26),
                   b=letters
                   )
test[,
  list(y=max(a)),
  by=b
][,
  ggplotDT(x=b, y=y) +
  geom_point() +
  scale_x_discrete("group") +
  scale_y_continuous("maximum") +
  coord_flip()
]

I would otherwise have to create an object specifically to contain the data
to plot, which often I find to be a superfluous step. But maybe that's just
me, and that's a minor point anyway.

By default, ggplot() (and more specifically aes()) looks only at two
environments: the global environment, and the data.frame provided as its
first argument. That means that with(DF, ggplot(, aes(...)) + ...) doesn't
work; neither does DT[, ggplot(, aes(...)) + ...]. With aesDT, provided in
my previous email, these uses become possible.


On Aug 14, 2011 11:34 PM, "Matthew Dowle" <mdowle at mdowle.plus.com> wrote:
>
> I'm not a ggplot2 expert by any means but I thought tests 167 and 168
> already tested compatibility. It needs to be called in the following
> way, though :
>
> DT <- data.table(a=1:10, b=1:10)
> ggplot(DT,aes(x=a,y=b))+geom_line()
>
> If you have ggplot2 loaded, then running test.data.table() should flash
> up the ggplot2 plots.
>
> Are these forms ok or am I missing something?
>
> Matthew
>
>
> On Sun, 2011-08-14 at 21:55 +0100, Timothée Carayol wrote:
>> Ah sorry -- the definition of ggplotDT() should be, of course:
>>
>>
>> ggplotDT <- function(...) {
>> ggplot(, aesDT(...))
>> }
>>
>>
>> (aes_now() was an artifact from Hadley Wickham's Stack Overflow tip)
>>
>>
>> t
>>
>>
>>
>> 2011/8/14 Timothée Carayol <timothee.carayol at gmail.com>
>> Hi,
>>
>> For some time I have been wishing that data.table and ggplot2
>> could play a bit nicer together.
>> For example, I would like this to work but it doesn't:
>>
>> > test <- data.table(a=1:10, b=1:10)
>> > test[, ggplot() + geom_line(aes(x=a, y=b))]
>> Error in eval(expr, envir, enclos) : object 'a' not found
>>
>> I spent a few dozen minutes trying to understand what was
>> going on (and stumbling upon this useful advice from Hadley
>> Wickham), and it turns out that it's very easy to fix (though
>> the fix is not very pretty).
>> Datatable-help, I present you with.. aesDT and ggplotDT.
>>
>>
>> aesDT <- function(...) {
>> aes <- structure(list(...), class = "uneval")
>> rename_aes(aes)
>> }
>>
>> Using aesDT() instead of aes() whenever you are in a
>> data.table (or in a with()) will now work. That is pretty much
>> all you need, but I thought I'd go just one tiny step further
>> with ggplotDT():
>>
>> ggplotDT <- function(...) {
>> ggplot(, aes_now(...))
>> }
>>
>> which makes the following possible:
>>
>> test[, ggplotDT(x=a, y=b) + geom_line()]
>>
>> i.e. put the aesthetics directly as arguments, saving a few
>> keystrokes and a pair of brackets.
>> Tiny problem that I have yet to solve: you now have to
>> explicitly give the name of all the aesthetics; aes() is
>> sufficiently clever to guess them if they're in the right
>> order, but the logic does not seem to carry over
>> straightforwardly to aesDT().
>>
>>
>> I know I'll be using these, so I thought maybe other people
>> here might be interested.
>>
>>
>> Timothee
>>
>>
>> _______________________________________________
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>>
https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help
>
>
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