Jeff,
>The X axis will be time in the format of hh:mm:ss ... can TGraph handle this?
I think so. My chart is also using time on the x-axis but I have been just letting the chart plot it one point per interval even though my times are not the same interval (they could be 5 times in one day, and zero in the next).
However, yours are one data point per second and thus all the intervals are the same so it should work fine for you. I don't know about labeling the increments in time format though. That could be a physical space issue too since each label is eight characters wide and I don't know if it handles vertical labels. I'm not even using labels on the x-axis on mine.
If you want to email me a sample list of data (say 25 points), I will see if I can put together a quick chart for you.
jbott at compuserve dot com
Regards,
James