elements that appear only once
another approach is: names(which(table(a) == 1)) but I don't know if you find this more elegant :) Best, Dimitris ---- Dimitris Rizopoulos Ph.D. Student Biostatistical Centre School of Public Health Catholic University of Leuven Address: Kapucijnenvoer 35, Leuven, Belgium Tel: +32/(0)16/336899 Fax: +32/(0)16/337015 Web: http://www.med.kuleuven.be/biostat/ http://www.student.kuleuven.be/~m0390867/dimitris.htm ----- Original Message ----- From: "Robin Hankin" <r.hankin at noc.soton.ac.uk> To: "RHelp" <r-help at stat.math.ethz.ch> Sent: Wednesday, February 22, 2006 10:11 AM Subject: [R] elements that appear only once
Hi. I have a factor and I want to extract just those elements that appear exactly once. How to do this? Toy example follows.
a <- as.factor(c(rep("oak",5) ,rep("ash",1),rep("elm",1),rep
("beech",4)))
a
[1] oak oak oak oak oak ash elm beech beech beech beech Levels: ash beech elm oak
table(a)
a
ash beech elm oak
1 4 1 5
So I would want "ash" and "elm", because there is only one ash and only one elm in my wood. My Best Effort:
names(table(a)[table(a)==1])
[1] "ash" "elm"
This doesn't seem particularly elegant to me; there must be a better way! anyone? -- Robin Hankin Uncertainty Analyst National Oceanography Centre, Southampton European Way, Southampton SO14 3ZH, UK tel 023-8059-7743
______________________________________________ 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
Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm