diff --git a/doc/rrdgraph_rpn.pod b/doc/rrdgraph_rpn.pod
index 16f7610f3d58abf1de276034437463cdc1b441c9..894fef16bbabcf42215946a1f880d8241d954f38 100644 (file)
--- a/doc/rrdgraph_rpn.pod
+++ b/doc/rrdgraph_rpn.pod
Pop two elements from the stack, compare them for the selected condition
and return 1 for true or 0 for false. Comparing an I<unknown> or an
-I<infinite> value will always result in 0 (false).
+I<infinite> value will result in I<unknown> returned ... which will also be
+treated as false by the B<IF> call.
B<UN, ISINF>
=item LAST, FIRST
-Return the last/first value including its time. The time for
-FIRST is actually the start of the corresponding interval, whereas
-LAST returns the end of the corresponding interval.
+Return the last/first non-nan or infinite value for the selected data
+stream, including its timestamp.
Example: C<VDEF:first=mydata,FIRST>