there is also colwise in the plyr package.
> library(plyr)
> colwise(class)(data6)
v13 v14 v15 f4 v16
1 integer numeric character factor logical
Justin
On Thu, Dec 29, 2011 at 4:47 PM, Jean V Adams <jvad...@usgs.gov> wrote:
> Dan Abner wrote on 12/29/2011 06:13:11 PM:
>
> > Hi everyone,
> >
> > I am attempting to use the apply() function to obtain the mode and class
> of
> > each column in a data frame, however, I am encountering unexpected
> results.
> > I have the following example data:
> >
> >
> > v13<-1:6
> > v14<-c(1,2,3,3,NA,1)
> > v15<-c("Good","Bad",NA,"Good","Bad","Bad")
> > f4<-factor(rep(c("Blue","Red","Green"),2))
> > v16<-c(F,T,F,F,T,F)
> > data6<-data.frame(v13,v14,v15,f4,v16)
> > data6
> >
> >
> > Here is my function definition:
> >
> >
> > contents<-function(x){
> > output<-data.frame(Varnum=1:ncol(x),
> > Name=names(x),
> > Mode=apply(x,2,mode),
> > Class=apply(x,2,class))
> > print(output)
> > }
>
>
> Use sapply() instead of apply(). In the help file for apply() it says: "
> If X is not an array but an object of a class with a non-null dim value
> (such as a data frame), apply attempts to coerce it to an array via
> as.matrix if it is two-dimensional (e.g., a data frame) or via as.array."
> This coercion to a matrix might be causing the unexpected result. sapply()
> and lapply() are designed specifically for lists (which a data frame is).
> I also simplified the function a bit ...
>
> contents<-function(x){
> data.frame(Varnum=1:ncol(x), Name=names(x),
> Mode=sapply(x,mode), Class=sapply(x,class))
> }
>
> Jean
>
>
> > ====
> >
> > When I call the function, I obtain the following:
> >
> >
> > > contents(data6)
> > Varnum Name Mode Class
> > v13 1 v13 character character
> > v14 2 v14 character character
> > v15 3 v15 character character
> > f4 4 f4 character character
> > v16 5 v16 character character
> >
> > =====
> >
> > Any help is appreciated.
> >
> > Thank you,
> >
> > Dan
> >
> > [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > 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.
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> 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.
>
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