[Rd] aggregate(as.formula("some formula"), data, function) error when called from in a function
Paul Bailey
pdbailey at umd.edu
Wed Jan 26 20:04:14 CET 2011
I'm having a problem with aggregate.formula when I call it in a function and the function is converted from a string in the funtion
I think my problem may also only occur when the left hand side of the formula is cbind(...)
Here is example code that generates a dataset and then the error.
The first function "agg2" fails
> agg2(FALSE)
do agg 2
Error in m[[2L]][[2L]] : object of type 'symbol' is not subsettable
but, if I run it have it return what it is going to pass to aggregate and pass it myself, it works. I can use this for a workaround (agg3) where one function does this itself.
I'm confused by the behavior. Is there some way to not have to use a separate function to make the call ?
======================
# start R code
# idea: in a function, count the number of instances
# of some factor (y) associated with another
# factor (x). aggregate.formula appears to be
# able to do this... but I have a problem if all of the following:
# (1) It is called in a function
# (2) the formula is created using as.formula(character)
# calling aggregate with the same formula (created with as.formula)
# outside the function works fine.
agg2 <- function(test=FALSE) {
# create a factor y
dat <- data.frame(y=sample(LETTERS[1:3],100,replace=TRUE))
# create a factor x
dat$x <- sample(letters[1:4],100,replace=TRUE)
# make a column of 1s and zeros
# 1 when that row has that level of y
# 0 otherwise
lvls <- levels(dat$y)
dat$ya <- 1*(dat[,1] == lvls[1])
dat$yb <- 1*(dat[,1] == lvls[2])
dat$yc <- 1*(dat[,1] == lvls[3])
# this works fine if you give the exact function
agg1 <- aggregate(cbind(ya,yb,yc)~x,data=dat,sum)
# and fine if you accept
fo <- as.formula("cbind(ya,yb,yc)~x")
if(test) {
return(list(fo=fo,data=dat))
}
cat("do agg 2\n")
agg2 <- aggregate(fo,data=dat,sum)
list(agg1,agg2)
}
agg2(FALSE)
ag <- agg2(TRUE)
ag$fo
aggregate(ag$fo,ag$data,sum)
agg3 <- function() {
ag <- agg2(TRUE)
ag$fo
aggregate(ag$fo,ag$data,sum)
}
agg3()
# end R code
==============
Paul Bailey
University of Maryland
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