11 messages · Lisa, Ista Zahn, PIKAL Petr +2 more
Dear All,
I just want to remove ?NA? from the levels of a factor. For example:
d<-data.frame(matrix(c("ww","ww","xx","yy","ww","yy","xx","yy","NA"),
ncol=3, byrow=TRUE))
factor(d[, 3], exclude=NA)
[1] xx yy NA Levels: NA xx yy But ?NA? is still listed in the levels. How can I solve this problem? Thanks in advance. Lisa -- View this message in context: http://r.789695.n4.nabble.com/Factor-function-tp3473984p3473984.html Sent from the R help mailing list archive at Nabble.com.
Hi Lisa, NA != "NA" The first represents a missing observation, the second represents a character string. HTH, Ista
Dear All,
I just want to remove ?NA? from the levels of a factor. ?For example:
d<-data.frame(matrix(c("ww","ww","xx","yy","ww","yy","xx","yy","NA"),
ncol=3, byrow=TRUE))
factor(d[, 3], exclude=NA)
[1] xx yy NA Levels: NA xx yy But ?NA? is still listed in the levels. How can I solve this problem? Thanks in advance. Lisa -- View this message in context: http://r.789695.n4.nabble.com/Factor-function-tp3473984p3473984.html Sent from the R help mailing list archive at Nabble.com.
______________________________________________ R-help at r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Ista Zahn Graduate student University of Rochester Department of Clinical and Social Psychology http://yourpsyche.org
Did you see the data frame "d"? Thanks. -- View this message in context: http://r.789695.n4.nabble.com/Factor-function-tp3473984p3474065.html Sent from the R help mailing list archive at Nabble.com.
Yes... did you understand that NA is not equal to "NA"? Best, Ista
Did you see the data frame "d"? Thanks. -- View this message in context: http://r.789695.n4.nabble.com/Factor-function-tp3473984p3474065.html Sent from the R help mailing list archive at Nabble.com.
______________________________________________ R-help at r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Ista Zahn Graduate student University of Rochester Department of Clinical and Social Psychology http://yourpsyche.org
Thank you for your reply again. I really know that NA is not "NA". I just want to figure out how to remove "NA" from the levels. Thanks again. -- View this message in context: http://r.789695.n4.nabble.com/Factor-function-tp3473984p3474127.html Sent from the R help mailing list archive at Nabble.com.
Dear All,
I just want to remove ?NA? from the levels of a factor. For example:
d<-data.frame(matrix(c("ww","ww","xx","yy","ww","yy","xx","yy","NA"),
ncol=3, byrow=TRUE))
factor(d[, 3], exclude=NA)
[1] xx yy NA Levels: NA xx yy But ?NA? is still listed in the levels. How can I solve this problem?
The column d[, 3] is already a factor. It is possible to avoid
this using
d<-data.frame(matrix(c("ww","ww","xx","yy","ww","yy","xx","yy","NA"),
ncol=3, byrow=TRUE), stringsAsFactors=FALSE)
Then, we get
factor(d[, 3], exclude="NA")
[1] xx yy <NA>
Levels: xx yy
Hope this helps.
Petr Savicky.
Thank you for your help. Your R code works well. Lisa -- View this message in context: http://r.789695.n4.nabble.com/Factor-function-tp3473984p3474196.html Sent from the R help mailing list archive at Nabble.com.
Hi
d<-data.frame(matrix(c("ww","ww","xx","yy","ww","yy","xx","yy","NA"),
ncol=3, byrow=TRUE))
Change character value "NA" to missing value <NA>
d[d[,3]=="NA",3]<-NA
If you want drop any unused levels of a factor just use
factor(d[,3])
[1] xx yy <NA>
Levels: xx yy
Regards
Petr
r-help-bounces at r-project.org napsal dne 25.04.2011 23:03:15:
Thank you for your reply again. I really know that NA is not "NA". I
just
want to figure out how to remove "NA" from the levels. Thanks again. -- View this message in context:
http://r.789695.n4.nabble.com/Factor-function-
tp3473984p3474127.html Sent from the R help mailing list archive at Nabble.com.
______________________________________________ R-help at r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Thank you so much! Lisa -- View this message in context: http://r.789695.n4.nabble.com/Factor-function-tp3473984p3475549.html Sent from the R help mailing list archive at Nabble.com.
Hi
d<-data.frame(matrix(c("ww","ww","xx","yy","ww","yy","xx","yy","NA"),
ncol=3, byrow=TRUE))
Change character value "NA" to missing value <NA>
d[d[,3]=="NA",3]<-NA
If you want drop any unused levels of a factor just use
factor(d[,3])
[1] xx yy <NA>
Levels: xx yy
An explicit NA is a good idea. If the NA is introduced before
creating the data frame, then also the data frame will not
contain the unwanted level.
a<-matrix(c("ww","ww","xx","yy","ww","yy","xx","yy","NA"),
ncol=3, byrow=TRUE)
a[a[,3]=="NA",3]<-NA
d<-data.frame(a)
d[,3]
[1] xx yy <NA>
Levels: xx yy
If the replacement should be done in the whole matrix, then
a[a=="NA"]<-NA
may be used.
Petr Savicky.
On Tue, Apr 26, 2011 at 10:51:33AM +0200, Petr PIKAL wrote:
Hi
d<-data.frame(matrix(c("ww","ww","xx","yy","ww","yy","xx","yy","NA"),
ncol=3, byrow=TRUE))
Change character value "NA" to missing value <NA>
d[d[,3]=="NA",3]<-NA
If you want drop any unused levels of a factor just use
factor(d[,3])
[1] xx yy <NA>
Levels: xx yy
An explicit NA is a good idea. If the NA is introduced before
creating the data frame, then also the data frame will not
contain the unwanted level.
a<-matrix(c("ww","ww","xx","yy","ww","yy","xx","yy","NA"),
ncol=3, byrow=TRUE)
a[a[,3]=="NA",3]<-NA
d<-data.frame(a)
d[,3]
[1] xx yy <NA>
Levels: xx yy
If the replacement should be done in the whole matrix, then
a[a=="NA"]<-NA
may be used.
Petr Savicky.
I think there's a buglet in here. According to the docs, "If exclude is used it should also be a factor with the same level set as x or a set of codes for the levels to be excluded". However, that plainly doesn't work:
cc <- c("x","y","NA")
ff <- factor(cc)
factor(ff,exclude=1)
[1] x y NA Levels: NA x y
factor(ff,exclude=ff[3])
[1] x y NA Levels: NA x y
factor(ff,exclude=ff[2])
[1] x y NA Levels: NA x y In these cases, the internal logic converts exclude to integer, and then uses match(levels, exclude) where levels is unique(x), i.e., a factor. This won't work because match() matches on the _character_ representation of x. The cleanest version that I can think of for the original problem is
factor(ff, levels=setdiff(levels(ff), "NA"))
[1] x y <NA> Levels: x y
Peter Dalgaard Center for Statistics, Copenhagen Business School Solbjerg Plads 3, 2000 Frederiksberg, Denmark Phone: (+45)38153501 Email: pd.mes at cbs.dk Priv: PDalgd at gmail.com