Steen Ladelund
2007-May-30 08:26 UTC
[R] Factor function: odd behavior when labels argument contains duplicates?
Hi all.
I think it would be nice to be able to combine levels of a factor on
creation a la
x <- rep(0:5,5)
y <- factor(x,levels=0:5,labels=c('1','1',2:5)) ## (1)
y
[1] 1 1 2 3 4 5 1 1 2 3 4 5 1 1 2 3 4 5 1 1 2 3 4 5 1 1 2 3 4 5
Levels: 1 1 2 3 4 5
I thougt this would (should?) create a factor with 5 levels, ie
combining 0 and 1 in x into one level in y.
I find it hard to predict the behavior of the following lines:
table(factor(y)) ## Odd ?
1 1 2 3 4 5
10 0 5 5 5 5
table(factor(factor(y))) ## This is what I want
1 2 3 4 5
10 5 5 5 5
It also seems strange that this should be the way to go:
levels(y) <- levels(y) ## Does what I want following (1) even tough
it appear to be a void statement?
y
y
[1] 1 1 2 3 4 5 1 1 2 3 4 5 1 1 2 3 4 5 1 1 2 3 4 5 1 1 2 3 4 5
Levels: 1 2 3 4 5
Am I missing an important point about factors or the factor function?
steen
Steen Ladelund, statistician
+4543233275 stelad01 at glostruphosp.kbhamt.dk
Research Center for Prevention and Health
Glostrup University Hospital, Denmark
www.fcfs.kbhamt.dk
Bill.Venables at csiro.au
2007-May-31 05:17 UTC
[R] Factor function: odd behavior when labels argument containsduplicates?
There is a difference between levels and labels. I think this is what you want.> x <- factor(rep(0:5, 2)) > x[1] 0 1 2 3 4 5 0 1 2 3 4 5 Levels: 0 1 2 3 4 5> levels(x) <- c(1,1:5) > x[1] 1 1 2 3 4 5 1 1 2 3 4 5 Levels: 1 2 3 4 5> table(x)x 1 2 3 4 5 4 2 2 2 2 Bill Venables CSIRO Laboratories PO Box 120, Cleveland, 4163 AUSTRALIA Office Phone (email preferred): +61 7 3826 7251 Fax (if absolutely necessary): +61 7 3826 7304 Mobile: (I don't have one!) Home Phone: +61 7 3286 7700 mailto:Bill.Venables at csiro.au http://www.cmis.csiro.au/bill.venables/ -----Original Message----- From: r-help-bounces at stat.math.ethz.ch [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Steen Ladelund Sent: Wednesday, 30 May 2007 6:27 PM To: r-help at stat.math.ethz.ch Subject: [R] Factor function: odd behavior when labels argument containsduplicates? Hi all. I think it would be nice to be able to combine levels of a factor on creation a la x <- rep(0:5,5) y <- factor(x,levels=0:5,labels=c('1','1',2:5)) ## (1) y [1] 1 1 2 3 4 5 1 1 2 3 4 5 1 1 2 3 4 5 1 1 2 3 4 5 1 1 2 3 4 5 Levels: 1 1 2 3 4 5 I thougt this would (should?) create a factor with 5 levels, ie combining 0 and 1 in x into one level in y. I find it hard to predict the behavior of the following lines: table(factor(y)) ## Odd ? 1 1 2 3 4 5 10 0 5 5 5 5 table(factor(factor(y))) ## This is what I want 1 2 3 4 5 10 5 5 5 5 It also seems strange that this should be the way to go: levels(y) <- levels(y) ## Does what I want following (1) even tough it appear to be a void statement? y y [1] 1 1 2 3 4 5 1 1 2 3 4 5 1 1 2 3 4 5 1 1 2 3 4 5 1 1 2 3 4 5 Levels: 1 2 3 4 5 Am I missing an important point about factors or the factor function? steen Steen Ladelund, statistician +4543233275 stelad01 at glostruphosp.kbhamt.dk Research Center for Prevention and Health Glostrup University Hospital, Denmark www.fcfs.kbhamt.dk ______________________________________________ R-help at stat.math.ethz.ch 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.