[R] (what I think are) two easy questions

[Rob Tirrell]

Hello,
I have a table of data (attachment) from which I am trying to generate a
graph.  I import the data into a vector (is that the right term? matrix
maybe), which seems to work fine except there is an X prepended to each
date.  This is my first problem.  My second is how would I make a graph of
the average weight of each group (PC3/CO, PC3/FO, FADU/CO, FADU/FO) vs.
time.  I would like each different groups weight to be differentiated in a
legend and all four displayed on one graph, with the dates as x values and
weight in grams as the y values.  I have been able to grasp much of R, but
for some reason this (simple to do in Excel or OpenOffice) evades me.
Thanks, Rob