[R] Removing constants from a data frame
David Forrest
drf5n at maplepark.com
Fri Sep 17 23:11:24 CEST 2004
Suppose I have
x<-data.frame(v1=1:4, v2=c(2,4,NA,7), v3=rep(1,4),
v4=LETTERS[1:4],v5=rep('Z',4))
or a much larger frame, and I wish to test for and remove the constant
numeric columns.
I made:
is.constant<-function(x){identical(min(x),max(x))}
and
apply(x,2,is.constant) # Works for numerics
x[,-which(apply(x,2,is.constant))]
I'd really like to be able to delete the constant columns without losing
my non-numerics. Ignoring the character columns would be OK.
Any suggestions?
Dave
--
Dave Forrest
drf at vims.edu (804)684-7900w
drf5n at maplepark.com (804)642-0662h
http://maplepark.com/~drf5n/
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