Graphational question

I would convert the timestamp, using strptime, i.e.

my.time <- strptime(my.cvs[[1]], "%H:%M")

This converts the strings into objects of R's POSIXlt class.

BTW: how do you like R-commander? For a while, I used RKWard, but this tended to crash on the most inconvenient times... The sycophancy is duly noted, no further efforts are necessary!