Sqldf questions in R studio

[jcblum]

@Lernst

To question 1, it doesn't work as well. That time is created from the following code: as.POSIXct(mydata$time,format="%Y-%m-%d %H:%M:%S",tz="America/New_York") The original format is factor.

when I check the new column by class(), it was shown as [1] "POSIXct" "POSIXt"

I'm afraid I'm not following what you mean. Can you post a reproducible example, so I can see what you're talking about?