The aggregate function applies FUN to vectors, not data frames. For example,
the default "mean" function accepts a vector such as a column in a data frame
and returns a scalar (well, a vector of length 1). Aggregate then calls this
function once for each piece of the column(s) you give it. Your function wants
two vectors, but aggregate does not understand how to give two inputs.
(In the future, please follow R-help mailing list guidelines and post using
plain text so your code does not get messed up.)
You could use split to break your data frame into a list of data frames, and
then sapply to extract the results you are looking for. I prefer to use the
plyr or dplyr or data.table packages to do all this for me.
d_rule <- function( DF ) {
i <- which( DF$a==max( DF$a ) )
if ( length( i ) == 1 ){
DF[ i, "x" ]
} else {
min( DF[ , "x" ] ) # did you mean min( DF$x[i] ) ?
}
}
dat <- data.frame( a=c(2,2,1,4,2,5,2,3,4,4)
, x = c(1:10)
, g = c(1,1,2,2,3,3,4,4,5,5)
)
# note that cbind on vectors creates a matrix
# in a matrix all columns must be of the same type
# but data frames generally have a variety of types
# so don't use cbind when making a data frame
library( dplyr )
result <- dat %>% group_by( g ) %>% do( answer = d_rule( . ) ) %>% as.data.frame
---------------------------------------------------------------------------
Jeff Newmiller The ..... ..... Go Live...
DCN:<jdnew...@dcn.davis.ca.us> Basics: ##.#. ##.#. Live Go...
Live: OO#.. Dead: OO#.. Playing
Research Engineer (Solar/Batteries O.O#. #.O#. with
/Software/Embedded Controllers) .OO#. .OO#. rocks...1k
---------------------------------------------------------------------------
Sent from my phone. Please excuse my brevity.
On March 4, 2015 2:02:06 PM PST, Typhenn Brichieri-Colombi via R-help
<r-help@r-project.org> wrote:
>Hello,
>
>I am trying to use the following custom function in an
>aggregatefunction, but cannot get R to recognize my data. I’ve read the
>help on function()and on aggregate() but am unable to solve my problem.
>How can I get R torecognize the data inputs for the custom function
>nested within aggregate()?
>
>My custom function is found below, as well as the errormessage I get
>when I run it on a test data set (I will be using this functionon a
>much larger dataset (over 600,000 rows))
>
>Thank you for your time and your help!
>
>
>
>d_rule<-function(a,x){
>
>i<-which(a==max(a))
>
>out<-ifelse(length(i)==1, x[i], min(x))
>
>return(out)
>
>}
>
>
>
>a<-c(2,2,1,4,2,5,2,3,4,4)
>
>x<-c(1:10)
>
>g<-c(1,1,2,2,3,3,4,4,5,5)
>
>dat<-as.data.frame(cbind(x,g))
>
>
>
>test<-aggregate(dat, by=list(g), FUN=d_rule,dat$a, dat$x)
>
>Error in dat$x : $ operator is invalid for atomic vectors
>
>
>
> [[alternative HTML version deleted]]
>
>______________________________________________
>R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
>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 -- To UNSUBSCRIBE and more, see
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.
