This is probably due to a numerical value that is coded as a factor. Have a look at the example below.
> In ggplot2 one line per group is plotted. The default grouping is the > combination of all factors. In the first example only B, in the second and > third example both A and B. This leaves just one observation per group and > hence the line cannot be displayed. > > You got that right Thierry. Year was char , on conversion to numeric I CAN see the lines. Many thanks to all of you guys: Sarah, Hadley and Thierry. I changed from desktop to my laptop hence the 64 bit to 32 bit. [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.