Hi:
Short answer: use one dot, not three:
> cast(french_fries, . ~ subject)
Using painty as value column. Use the value argument to cast to
override this choice
Aggregation requires fun.aggregate: length used as default
value 3 10 15 16 19 31 51 52 63 78 79 86
1 (all) 54 60 60 60 60 54 60 60 60 60 54 54
Long answer:
It's the same as using . in a model formula. The ... construct is used
as a formal argument in a function *definition* to allow passage of
needed arguments in a function call that are not part of the list of
formal arguments. I noticed
> args(cast)
function (data, formula = ... ~ variable, fun.aggregate = NULL,
..., margins = FALSE, subset = TRUE, df = FALSE, fill = NULL,
add.missing = FALSE, value = guess_value(data))
so I can see where you may have gotten confused. Here's an example
using the same data frame where the ... argument comes into play:
# melt the response variables (the sensory attributes) into
# a factor variable for the attributes themselves and a value
# variable for their corresponding values.
ffm <- melt(french_fries, id = c('subject', 'time', 'treatment', 'rep'))
head(ffm)
# Recast the data so that the average score per subject/treatment
score is produced.
# However, there are NAs in the data frame, so we need to pass na.rm = TRUE:
cast(ffm, subject + treatment ~ variable, value_var = 'value',
fun.aggregate = 'mean', na.rm = TRUE)
# To average over all subjects, treatments, times and reps,
cast(ffm, . ~ variable, value_var = 'value', fun.aggregate = 'mean',
na.rm = TRUE)
value potato buttery grassy rancid painty
1 (all) 6.952518 1.823699 0.6641727 3.85223 2.521758
na.rm is not part of the formal argument list to cast(), but because
the ... construct is present, we can pass na.rm = TRUE to the mean()
function used to aggregate the data in the actual call. Observe that
> args(mean.default)
function (x, trim = 0, na.rm = FALSE, ...)
so the na.rm = TRUE argument in the call to cast() is actually passed to mean().
[To understand how this works, you need to do some study about
function writing; the R Language Definition manual is one place where
this is described in detail. The formal arguments to mean.default()
are x, trim, na.rm and ...; trim and na.rm have default values 0 and
FALSE than can be overridden in an actual call to that function.]
You should never need to use ... in an actual function call; in a
formula, use of . on one side of ~ means to use all variables in the
data frame except those used on the other side (the side where one or
more variables are specified). For example, in a linear regression
context,
lm(y ~ ., data = mydata)
would use all variables in mydata except y as covariates in the model.
HTH,
Dennis
On Thu, Jun 9, 2011 at 12:10 AM, misterbray <misterb...@gmail.com> wrote:
> Whenever I use "..." in the formula of the cast function, from the reshape
> package, I get the following error:
>
> Error in `[.data.frame`(data, , variables, drop = FALSE) :
> undefined columns selected
>
>
> For example:
>
> data(french_fries) #available in the reshape package
>> head(french_fries)
> time treatment subject rep potato buttery grassy rancid painty
> 61 1 1 3 1 2.9 0.0 0.0 0.0 5.5
> 25 1 1 3 2 14.0 0.0 0.0 1.1 0.0
> 62 1 1 10 1 11.0 6.4 0.0 0.0 0.0
> 26 1 1 10 2 9.9 5.9 2.9 2.2 0.0
> 63 1 1 15 1 1.2 0.1 0.0 1.1 5.1
> 27 1 1 15 2 8.8 3.0 3.6 1.5 2.3
>
>>cast(french_fries, ...~ subject)
> Using painty as value column. Use the value argument to cast to override
> this choice
> Error in `[.data.frame`(data, , variables, drop = FALSE) :
> undefined columns selected
>
>
>
>
> --
> View this message in context:
> http://r.789695.n4.nabble.com/Reshape-cast-error-using-in-formula-expression-tp3584721p3584721.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
