isdefined gives warning if undefined ?

In a loop, I'm trying to specify the plot Y min/max for certain
variables and allow the min/max of others to be automatically chosen
for others. My understanding is that doing so requires trYmin and
trYmax to be defined and undefined for the two different cases. (The
documenation actually says that the attributes should not be
"specified", which I assume means undefined.) But when I try using
      if( isdefined(xyres_at_trYMinF) ) then
         undef(xyres_at_trYMinF)
      end if
I get the message
  "warning:Attempt to reference attribute (trYMinF) which is undefined"
from the if test when xyres_at_trYMinF is undefined (duh). Why does it
give a warning when the whole idea is to find out whether the
variable is defined or not !?

                    Jack

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Received on Thu Aug 31 2006 - 20:42:31 MDT