Archive interpolation mode question

[Michal Kara <lemming@xxxxxxxxxxxxxxxxxxx>]

   Hello!

   I have added archive mode to PCPMON. It works fine, but when I use the
"interpolation" mode, PCP refuses to fetch first two (or three?) metrics
from the archive. I guess it is because the interpolation algorithm needs few
previous values, I just want to be sure. 

                                        Thanks,
                                           Michal Kara

P.S.: If it is as I think, it would be nice to leave a note in pmSetMode(3)
manpage.