[R] reading in columns of a data set as factors

[Faheem Mitha]

Dear Dr. Kleiber,

Just to make sure I understand this. lapply acts on lists.  In the line
below, are we regarding mydat[ ,1:66] as a list with 66 components?  How
is lapply happy to regard this as a list?  I have only the dimmest
understanding of how classes are inherited by subsets of objects, but
class(mydat[ ,1:66]) gives data.frame, and is a data frame also a list?

                                                  Faheem.

> mydat[,1:66] _ lapply(mydat[,1:66],as.facto

On Thu, 27 Apr 2000, Faheem Mitha wrote:

> Thanks, this was exactly what I was looking for. Specifically, the last
> line:
> 
> > mydat[,1:66] _ lapply(mydat[,1:66],as.factor
> 
> can be used the replace the loop I have, and is much faster. Didn't think
> of using lapply. Must get to know it better. Looks like a useful
> all-purpose function.
>                                                Faheem.
> 
> On Thu, 27 Apr 2000, Pierre Kleiber wrote:
> 
> > Here's how I would go about it:
> > 
> > > mydat <- as.data.frame(matrix(scan("input.dat"),byrow=T,ncol=99)
> > > names(mydat) _ c(paste("b",1:66,sep=""),paste("x",1:33,sep=""))
> > > mydat[,1:66] _ lapply(mydat[,1:66],as.factor)
> 
> 

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