Hello, I found rather surprising the behaviour of POSIXct and POSIXlt classes when combined with min and tapply.
The details can be deduced from the script below: ############# Start of the script #################### before <- Sys.time() Sys.sleep( 1 ) now1 <- now2 <- Sys.time() my.times <- c( before, now1, now2 ) class( my.times ) ## [1] "POSIXct" "POSIXt" min( my.times ) ## [1] "2010-10-28 18:52:17 CEST" ### So far, so good... but: my.period <- c( "a", "b", "b" ) tapply( my.times, my.period, min ) ## a b ## 1288284737 1288284780 ## Where did my POSIXct class go? my.times.lt <- as.POSIXlt( my.times ) min( my.times.lt ) ## [1] "2010-10-28 18:52:17 CEST"; good! tapply( my.times.lt, my.period, min ) # $a # [1] 17.449 # # $b # [1] 52 # # Mensajes de aviso perdidos # In ansmat[index] <- ans : # número de items para para sustituir no es un múltiplo de la longitud del reemplazo # # ¿? :( ############# End of the script #################### Here are the details of my session (as reported by sessionInfo): R version 2.12.0 (2010-10-15) Platform: i386-pc-mingw32/i386 (32-bit) locale: [1] LC_COLLATE=Spanish_Spain.1252 LC_CTYPE=Spanish_Spain.1252 LC_MONETARY=Spanish_Spain.1252 LC_NUMERIC=C [5] LC_TIME=Spanish_Spain.1252 attached base packages: [1] stats graphics grDevices utils datasets methods base other attached packages: [1] RODBC_1.3-2 plotrix_3.0 loaded via a namespace (and not attached): [1] tools_2.12.0 I am running R on a Windows XP Box. Thank you very much, Carlos J. Gil Bellosta http://www.datanalytics.com ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel