Trend graph

Dear R Gurus,

I have a problem related to plot.
For example, I have two variables, pre and post.

pre <- c(1,2,3,4,5)
post <- c(2,5,7,2,3)

How can I plot a line graph similar to this one?

http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1847566&rendertype=figure&id=F1

Would you please provide me a keyword so that I can search. I don't
know what is the name of this type of graph.

Regards,
H

CH Chan
Research Assistant - KWH
http://www.macgrass.com