Dear R users, My immediate problem is that I do not seem to understand how to use the function scale_x_datetime function in ggplot. My deeper problem is that I don’t understand the use of the POSIXct class. My data looks like like the following : T val 2009-11-04 23:59:57 972.357117 2009-11-05 00:02:21 969.389221 2009-11-05 00:04:45 868.817749 2009-11-05 00:07:09 805.593079 2009-11-05 00:09:33 928.946106 2009-11-05 00:11:57 1004.880249 2009-11-05 00:14:21 969.154846 2009-11-05 00:16:45 989.090942 2009-11-05 00:19:09 1009.907837 2009-11-05 00:21:33 1058.458374 2009-11-05 00:23:57 1179.298096 ……………… ………………. 2009-11-06 23:57:23 650.345631 I attempted to code with the following : df<-read.table(file=file1,header=TRUE,sep="\t",colClasses=c("character","numeric")) # Could not directly read in the time with the POSIXct class instead of as character t1<-as.POSIXct(df$T) # interested in a specific time frame # first attempted without the CET in the limits lim2<- c("2009-11-05 12:00:00 CET","2009-11-06 13:00:00 CET") library(ggplot) ggplot(data=df,aes(x=T,y=val))+geom_line()+scale_x_datetime(limits=lim2,format="%H") I get the following error message : ##### Error in if (length(range) == 1 || diff(range) == 0) { : missing value where TRUE/FALSE needed In addition: Warning message: In get("transform", env = trans, inherits = TRUE)(trans, ...) : NAs introduced by coercion ###### I next tried to get a subset of the dataframe with the following : df2<-df [df$T>"2009-11-05 11:57:33 CET" & df$T<"2009-11-06 12:59:57 CET",] > head(df2) [1] Tid1 Rok <0 rows> (or 0-length row.names) I don’t seem to understand how I should work with the POSIXct class. And, this is just the first step in my analysis (with many more steps pending).. I will appreciate any and all the help that I can get. Thanking you, Ravi
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