Hi,You haven't provided any example dataset. set.seed(42) dat1 <- data.frame(dates=seq(as.POSIXct("2009-01-01 00:00:00",format="%Y-%m-%d %H:%M:%S"),by= '12 hour', length=12),Field1=rnorm(12),Field2=LETTERS[1:12])
set.seed(395) dat2 <- data.frame(dates=seq(as.POSIXct("2009-01-01 00:00:00",format="%Y-%m-%d %H:%M:%S"),by= '6 hour', length=12),Field1=rnorm(12),Field2=sample(LETTERS,12,replace=FALSE)) merge(dat1,dat2,by="dates") # dates Field1.x Field2.x Field1.y Field2.y #1 2009-01-01 00:00:00 1.3709584 A -1.2152900 V #2 2009-01-01 12:00:00 -0.5646982 B -1.2771657 P #3 2009-01-02 00:00:00 0.3631284 C 0.4829300 W #4 2009-01-02 12:00:00 0.6328626 D 0.5468625 Y #5 2009-01-03 00:00:00 0.4042683 E -1.7113256 I #6 2009-01-03 12:00:00 -0.1061245 F 0.4851851 B merge(dat1,dat2,by="dates",all=TRUE)[1:5,] dates Field1.x Field2.x Field1.y Field2.y 1 2009-01-01 00:00:00 1.3709584 A -1.2152900 V 2 2009-01-01 06:00:00 NA <NA> -0.4633211 G 3 2009-01-01 12:00:00 -0.5646982 B -1.2771657 P 4 2009-01-01 18:00:00 NA <NA> 0.6011199 N 5 2009-01-02 00:00:00 0.3631284 C 0.4829300 W A.K. why wont two tables merge correctly on a date? I have one table with a field called 'date' "2009-01-01 00:00:00". The other table also has a field call 'date'. The dates are something like "2009-01-01 01:00:00". The two tables are not merging correctly. The dates are not lining up. <NA> The table also has other fields with dates in them. Sorry the data set is very big so I have not loaded it. The code I'm using to merge is m2 <- merge(m1 ,mt,all=TRUE) ______________________________________________ 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.