CDEF operators SHIFT, SQRT, SORT, and REV (reverse). See documentation for what

[rrdtool.git] / doc / rrdgraph_rpn.src

diff --git a/doc/rrdgraph_rpn.src b/doc/rrdgraph_rpn.src
index 65f0917..ae1a91b 100644 (file)
--- a/doc/rrdgraph_rpn.src
+++ b/doc/rrdgraph_rpn.src
@@ -1,6 +1,6 @@
 =include name
 
-=head1 SYNOPSYS
+=head1 SYNOPSIS
 
 I<E<lt>RPN expressionE<gt>> := 
 I<E<lt>vnameE<gt>>|I<E<lt>operatorE<gt>>|I<E<lt>valueE<gt>>
@@ -94,9 +94,9 @@ B<+, -, *, /, %>
 
 Add, subtract, multiply, divide, modulo
 
-B<SIN, COS, LOG, EXP>
+B<SIN, COS, LOG, EXP, SQRT>
 
-Sine, cosine (input in radians), log, exp (natural logarithm)
+Sine, cosine (input in radians), log, exp (natural logarithm), square root
 
 B<ATAN>
 
@@ -108,6 +108,18 @@ Round down,up to the nearest integer
 
 Z<>
 
+=item Ordering Operations
+
+B<SORT, REV>
+
+Pop one element from the stack.  This is the I<count> of items to be sorted
+(or reversed).  The top I<count> of the remaining elements are then sorted
+(or reversed) in place on the stack.
+
+Example: C<CDEF:x=v1,v2,v3,v4,v5,v6,6,SORT,POP,5,REV,POP,+,+,+,4,/> will
+compute the average of the values v1..v6 after removing the smallest and
+largest.
+
 =item Special values
 
 B<UNKN>
@@ -205,7 +217,7 @@ Z<>
 =item MAXIMUM, MINIMUM, AVERAGE
 
 Return the corresponding value, MAXIMUM and MINIMUM also return
-the first occurance of that value in the time component.
+the first occurrence of that value in the time component.
 
 Example: C<VDEF:avg=mydata,AVERAGE>
 
@@ -215,7 +227,7 @@ Z<>
 
 Return the last,first value including its time.  The time for
 FIRST is actually the start of the corresponding interval, where
-LASTs time component returns the end of the corresponding interval.
+the LAST time component returns the end of the corresponding interval.
 
 Example: C<VDEF:first=mydata,FIRST>
 
@@ -223,7 +235,7 @@ Z<>
 
 =item TOTAL
 
-Returns the rate from each defined timeslot multiplied with the
+Returns the rate from each defined time slot multiplied with the
 step size.  This can for instance return total bytes transfered
 when you have logged bytes per second. The time component returns
 the amount of seconds