On Nov 11, 2009, at 9:00 PM, Daniel Malter wrote:
#I have a data frame with a numeric and a character variable.
x=c(1,2,3,2,0,2,-1,-2,-4)
md=c(rep("Miller",3), rep("Richard",3),rep("Smith",3))
data1=data.frame(x,md)
#I subset this data.frame in a way such that one level of the
character
variable does not appear in the new dataset.
data2=data1[x>0,]
data3=subset(data1,x>0)
I thought this was asked and answered yesterday ((???)):
> data2 <- as.data.frame(lapply(data2, function(x) x[,drop=TRUE]))
> data2
x md
1 1 Miller
2 2 Miller
3 3 Miller
4 2 Richard
5 2 Richard
> data3 <- as.data.frame(lapply(data3, function(x) x[,drop=TRUE]))
> data3
x md
1 1 Miller
2 2 Miller
3 3 Miller
4 2 Richard
5 2 Richard
> unique(data2$md)
[1] Miller Richard
Levels: Miller Richard
> unique(data3$md)
[1] Miller Richard
Levels: Miller Richard
--
David
#However, when I check the levels of the factor variable in the
subset data
frame, it still shows the levels that are now unused.
unique(data2$md)
unique(data3$md)
#This leads to complications in table and tapply that I want to avoid.
table(data2$md)
tapply(data2$x,data2$md,mean)
table(data3$md)
tapply(data3$x,data3$md,mean)
#Basically, I want to completely remove "Smith" from data frame
data2 or
data3 so that it would not show up in table or tapply operations.
Thanks for any pointers,
Daniel
-----------------------------------------------
"Who has visions, should see a doctor,"
Helmut Schmidt, German Chancellor (1974-1982).
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David Winsemius, MD
Heritage Laboratories
West Hartford, CT
______________________________________________
R-help@r-project.org mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
