You could convert those columns to "Date" class by:
Data[,c(4,6)]<-lapply(Data[,c(4,6)],as.Date,origin="1970-01-01") #or Data[,c(4,6)]<-lapply(Data[,c(4,6)],function(x) structure(x,class="Date")) # dat1 dat2 Dat1a Dat1b Dat2a Dat2b #1 41327 41327 2013-02-22 2013-02-22 2013-02-22 2013-02-22 #2 41334 41334 2013-03-01 2013-03-01 2013-03-01 2013-03-01 #3 41341 41341 2013-03-08 2013-03-08 2013-03-08 2013-03-08 #4 41348 41348 2013-03-15 2013-03-15 2013-03-15 2013-03-15 #5 41355 NA 2013-03-22 2013-03-22 <NA> <NA> #6 41362 41362 2013-03-29 2013-03-29 2013-03-29 2013-03-29 #7 41369 41369 2013-04-05 2013-04-05 2013-04-05 2013-04-05 #8 41376 41376 2013-04-12 2013-04-12 2013-04-12 2013-04-12 #9 41383 NA 2013-04-19 2013-04-19 <NA> <NA> #10 41390 41390 2013-04-26 2013-04-26 2013-04-26 2013-04-26 #11 41397 41397 2013-05-03 2013-05-03 2013-05-03 2013-05-03 A.K. ----- Original Message ----- From: Denis Chabot <chabot.de...@gmail.com> To: R-help@r-project.org Cc: Sent: Thursday, May 23, 2013 5:35 PM Subject: [R] subsetting and Dates Hi, I am trying to understand why creating Date variables does not work if I subset to avoid NAs. I had problems creating these Date variables in my code and I thought that the presence of NAs was the cause. So I used a condition to avoid NAs. It turns out that NAs are not a problem and I do not need to subset, but I'd like to understand why subsetting causes the problem. The strange numbers I start with are what I get when I read an Excel sheet with the function read.xls() from package gdata. dat1 = c(41327, 41334, 41341, 41348, 41355, 41362, 41369, 41376, 41383, 41390, 41397) dat2 = dat1 dat2[c(5,9)]=NA Data = data.frame(dat1,dat2) keep1 = !is.na(Data$dat1) keep2 = !is.na(Data$dat2) Data$Dat1a = as.Date(Data[,"dat1"], origin="1899-12-30") Data$Dat1b[keep1] = as.Date(Data[keep1,"dat1"], origin="1899-12-30") Data$Dat2a = as.Date(Data[,"dat2"], origin="1899-12-30") Data$Dat2b[keep2] = as.Date(Data[keep2,"dat2"], origin="1899-12-30") Data dat1 dat2 Dat1a Dat1b Dat2a Dat2b 1 41327 41327 2013-02-22 15758 2013-02-22 15758 2 41334 41334 2013-03-01 15765 2013-03-01 15765 3 41341 41341 2013-03-08 15772 2013-03-08 15772 4 41348 41348 2013-03-15 15779 2013-03-15 15779 5 41355 NA 2013-03-22 15786 <NA> NA 6 41362 41362 2013-03-29 15793 2013-03-29 15793 7 41369 41369 2013-04-05 15800 2013-04-05 15800 8 41376 41376 2013-04-12 15807 2013-04-12 15807 9 41383 NA 2013-04-19 15814 <NA> NA 10 41390 41390 2013-04-26 15821 2013-04-26 15821 11 41397 41397 2013-05-03 15828 2013-05-03 15828 So variables Dat1b and Dat2b are not converted to Date class. sessionInfo() R version 2.15.2 (2012-10-26) Platform: x86_64-apple-darwin9.8.0/x86_64 (64-bit) locale: [1] fr_CA.UTF-8/fr_CA.UTF-8/fr_CA.UTF-8/C/fr_CA.UTF-8/fr_CA.UTF-8 attached base packages: [1] stats graphics grDevices utils datasets methods base other attached packages: [1] gdata_2.12.0 loaded via a namespace (and not attached): [1] gtools_2.7.0 Thanks in advance, Denis ______________________________________________ R-help@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. ______________________________________________ R-help@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.
