datetime.R

# Conversion of unix timestamps to POSIXct

> as.POSIXct(1388512551, origin="1970-01-01 00:00:00")
[1] "2013-12-31 19:55:51 SAST"

# ggplot of POSIXct. 
# pdt_time is of POSIXct type
> m <- ggplot(df, aes(pdt_time, some_count)) + geom_point(aes(colour=as.factor(some_factor)))
> m

# Pretty printing datetimes. Major breaks with an axis label every 30 minutes
> m <- m + scale_x_datetime(breaks = date_breaks("30 min"),  labels = date_format("%H:%M"))

# Rotate the text labels. Decongests the x axis labels
> m <- m + opts(axis.text.x=theme_text(angle=90, hjust=1))