John -
You can use a syntax similar to what you've tried with
the select= argument of the subset function:
subset(dfxyz,select=-y)
x z
1 1 0
2 2 0
. . .
subset(dfxyz,select=-z)
x y
1 1 11
2 2 12
. . .
- Phil Spector
Statistical Computing Facility
Department of Statistics
UC Berkeley
spec...@stat.berkeley.edu
On Sun, 26 Dec 2010, John Sorkin wrote:
I am trying to drop a column of a data frame. The code below attempts to drop a
numeric column (which does not work but gives no error or warning) and a factor
column (which does not work but gives an error).
I would appreciate someone telling me why my code does not work, and suggesting
code that will work.
Thanks,
John
rm(dfxyz,dfxz,dfxy)
# create the data frame.
dfxyz <- data.frame(x=1:10,y=11:20,z=factor(c(rep(0,5),rep(1,5))))
dfxyz
names(dfxyz)
# try to drop y column
# does not work, does not produce error message
dfxz <- dfxyz[,-(dfxyz$y)]
dfxz
# try to drop z column
# does not work, produces error message:
# In Ops.factor(df$z) : - not meaningful for factors
dfxy <- dfxyz[,-dfxyz$z]
dfxy
John David Sorkin M.D., Ph.D.
Chief, Biostatistics and Informatics
University of Maryland School of Medicine Division of Gerontology
Baltimore VA Medical Center
10 North Greene Street
GRECC (BT/18/GR)
Baltimore, MD 21201-1524
(Phone) 410-605-7119
(Fax) 410-605-7913 (Please call phone number above prior to faxing)
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