be clearer as to what VDEF LAST/FIRST do.

[rrdtool.git] / doc / rrdgraph_rpn.pod

diff --git a/doc/rrdgraph_rpn.pod b/doc/rrdgraph_rpn.pod
index b6b68e3..894fef1 100644 (file)
--- a/doc/rrdgraph_rpn.pod
+++ b/doc/rrdgraph_rpn.pod
@@ -51,7 +51,8 @@ B<LT, LE, GT, GE, EQ, NE>
 
 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>
 
@@ -253,7 +254,7 @@ rrdtool graph image.png --imgformat=PNG \
  TICK:exceeds#aa000080:1
 
 Note: Experience has shown that a factor between 3 and 5 to scale sigma is a good 
-discriminator to detect abnormal behaviour. This obviously depends also on the type 
+discriminator to detect abnormal behavior. This obviously depends also on the type 
 of data and how "noisy" the data series is.
 
 This prediction can only be used for short term extrapolations - say a few days into the future-
@@ -343,16 +344,15 @@ Example: C<VDEF:stdev=mydata,STDEV>
 
 =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>
 
 =item TOTAL
 
 Returns the rate from each defined time slot multiplied with the
-step size.  This can, for instance, return total bytes transfered
+step size.  This can, for instance, return total bytes transferred
 when you have logged bytes per second. The time component returns
 the number of seconds.
 
@@ -401,4 +401,5 @@ Make sure to read L<rrdgraph_examples> for tipsE<amp>tricks.
 
 Program by Tobias Oetiker E<lt>tobi@oetiker.chE<gt>
 
-This manual page by Alex van den Bogaerdt E<lt>alex@ergens.op.het.netE<gt>
+This manual page by Alex van den Bogaerdt E<lt>alex@vandenbogaerdt.nlE<gt>
+with corrections and/or additions by several people