Please keep r-help in cc. Yes. Have a look at this example
ifelse( sample(c(TRUE, FALSE), size = 0.5 * length(letters), replace = TRUE), letters, LETTERS ) ir. Thierry Onkelinx Instituut voor natuur- en bosonderzoek / Research Institute for Nature and Forest team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance Kliniekstraat 25 1070 Anderlecht Belgium To call in the statistician after the experiment is done may be no more than asking him to perform a post-mortem examination: he may be able to say what the experiment died of. ~ Sir Ronald Aylmer Fisher The plural of anecdote is not data. ~ Roger Brinner The combination of some data and an aching desire for an answer does not ensure that a reasonable answer can be extracted from a given body of data. ~ John Tukey 2016-06-14 17:31 GMT+02:00 Ayyappa Chaturvedula <ayyapp...@gmail.com>: > Thank you very much for your kind support. The length of my condition > vector is ~80 because I want only Sex==1 and else will be the other. I > understand now how ifelse works. If the vector of the simulated vector is > longer than the condition vector, then it takes the first few elements to > match the length of condition vector and discards the rest? > > Regards, > Ayyappa > > On Tue, Jun 14, 2016 at 10:15 AM, Thierry Onkelinx < > thierry.onkel...@inbo.be> wrote: > >> Dear Ayyappa, >> >> ifelse works on a vector. See the example below. >> >> ifelse( >> sample(c(TRUE, FALSE), size = length(letters), replace = TRUE), >> letters, >> LETTERS >> ) >> >> However, note that it will recycle short vectors when they are not of >> equal length. >> >> ifelse( >> sample(c(TRUE, FALSE), size = 2 * length(letters), replace = TRUE), >> letters, >> LETTERS >> ) >> >> In your code the length of the condition vector is 200, the length of the >> two other vectors is 100. >> >> Best regards, >> >> ir. Thierry Onkelinx >> Instituut voor natuur- en bosonderzoek / Research Institute for Nature >> and Forest >> team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance >> Kliniekstraat 25 >> 1070 Anderlecht >> Belgium >> >> To call in the statistician after the experiment is done may be no more >> than asking him to perform a post-mortem examination: he may be able to say >> what the experiment died of. ~ Sir Ronald Aylmer Fisher >> The plural of anecdote is not data. ~ Roger Brinner >> The combination of some data and an aching desire for an answer does not >> ensure that a reasonable answer can be extracted from a given body of data. >> ~ John Tukey >> >> 2016-06-14 17:02 GMT+02:00 Ayyappa Chaturvedula <ayyapp...@gmail.com>: >> >>> Dear Group, >>> >>> I am trying to simulate a dataset with 200 individuals with random >>> assignment of Sex (1,0) and Weight from lognormal distribution specific >>> to >>> Sex. I am intrigued by the behavior of rlnorm function to impute a value >>> of Weight from the specified distribution. Here is the code: >>> ID<-1:200 >>> Sex<-sample(c(0,1),200,replace=T,prob=c(0.4,0.6)) >>> fulldata<-data.frame(ID,Sex) >>> fulldata$Wt<-ifelse(fulldata$Sex==1,rlnorm(100, meanlog = log(85.1), >>> sdlog >>> = sqrt(0.0329)), >>> rlnorm(100, meanlog = log(73), sdlog = sqrt(0.0442))) >>> >>> mean(fulldata$Wt[fulldata$Sex==0]);to check the mean is close to 73 >>> mean(fulldata$Wt[fulldata$Sex==1]);to check the mean is close to 85 >>> >>> I see that the number of simulated values has an effect on the mean >>> calculated after imputation. That is, the code rlnorm(100, meanlog = >>> log(73), sdlog = sqrt(0.0442)) gives much better match compared to >>> rlnorm(1, meanlog = log(73), sdlog = sqrt(0.0442)) in ifelse statement in >>> the code above. >>> >>> My understanding is that ifelse will be imputing only one value where the >>> condition is met as specified. I appreciate your insights on the >>> behavior >>> for better performance of increasing sample number. I appreciate your >>> comments. >>> >>> Regards, >>> Ayyappa >>> >>> [[alternative HTML version deleted]] >>> >>> ______________________________________________ >>> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see >>> 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. >>> >> >> > [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
