[R] how to convert all columns of a data frame into factors

[Gavin Simpson]

On Wed, 2006-10-04 at 17:04 +0100, Gavin Simpson wrote:
> On Wed, 2006-10-04 at 11:33 -0400, Weiwei Shi wrote:
> > Hi,
> > 
> > I use "apply"
> > apply(x, 2, factor)
> > 
> > but it does not work. please help. thanks.
> > 

Ah, lesson one: read the email clearly before replying - just like my
old Geography teacher used to tell me!

This works

dat <- sample(LETTERS, 100, replace = TRUE)
# use a data. frame not a matrix
dat <- data.frame(matrix(dat, ncol = 10))
dat
lapply(dat, factor) # as a list
# or, as a data.frame
data.frame(lapply(dat, factor))

G

> 
> In what sense does it not work? And how can you possibly expect anyone
> on this list to help you as you neither supply the error message you
> received nor provide us with x or a reproducible example, nor tell us
> what you want to achieve.
> 
> E.g.
> 
> dat <- sample(LETTERS, 100, replace = TRUE)
> dat <- matrix(dat, ncol = 10)
> dat
> apply(dat, 2, factor)
> 
> which appears to be converting a character vector into a factor, which
> is then coerced to a numeric vector (as there are only numeric and
> character matrices in R) - but I may be wrong:
> 
> as.numeric(factor(dat[,1]))
>  [1] 7 7 2 5 8 1 4 7 3 6
> 
> which is the first column of the object returned by apply(dat, 2,
> factor). Is this not what you wanted?
> 
> So perhaps you could provide the list with some further information as
> you are asked to in the posting guide!
> 
> HTH
> 
> G
-- 
%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%
 Gavin Simpson                 [t] +44 (0)20 7679 0522
 ECRC & ENSIS, UCL Geography,  [f] +44 (0)20 7679 0565
 Pearson Building,             [e] gavin.simpsonATNOSPAMucl.ac.uk
 Gower Street, London          [w] http://www.ucl.ac.uk/~ucfagls/
 UK. WC1E 6BT.                 [w] http://www.freshwaters.org.uk
%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%