On 8/1/2008 4:49 AM, David Hajage wrote:
Hello R users,
I run this code under windows XP and R 2.7.1 :
head(esoph)
agegp alcgp tobgp ncases ncontrols
1 25-34 0-39g/day 0-9g/day 0 40
2 25-34 0-39g/day 10-19 0 10
3 25-34 0-39g/day 20-29 0 6
4 25-34 0-39g/day 30+ 0 5
5 25-34 40-79 0-9g/day 0 27
6 25-34 40-79 10-19 0 7
class(esoph$agegp)
[1] "ordered" "factor"
class(esoph$alcgp)
[1] "ordered" "factor"
class(esoph$tobgp)
[1] "ordered" "factor"
class(esoph$ncases)
[1] "numeric"
class(esoph$ncontrols)
[1] "numeric"
apply(esoph, 2, class)
agegp alcgp tobgp ncases ncontrols
"character" "character" "character" "character" "character"
I don't understand why the result is all "character"...
Because the data frame is coerced to a matrix by apply():
"If X is not an array but has a dimension attribute, apply attempts to
coerce it to an array via as.matrix if it is two-dimensional (e.g., data
frames)..."
Try lapply() or sapply() instead.
> lapply(esoph, class)
$agegp
[1] "ordered" "factor"
$alcgp
[1] "ordered" "factor"
$tobgp
[1] "ordered" "factor"
$ncases
[1] "numeric"
$ncontrols
[1] "numeric"
Thanks a lot.
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