paramters in SHIFT are separated by : like everywhere else

[rrdtool.git] / doc / rrdgraph_rpn.src

diff --git a/doc/rrdgraph_rpn.src b/doc/rrdgraph_rpn.src
index a8c4b11..4aad477 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 +94,13 @@ 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>
+
+Arctangent. Output in radians.
 
 B<FLOOR, CEIL>
 
@@ -104,6 +108,42 @@ Round down,up to the nearest integer
 
 Z<>
 
+=item Set 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.
+
+B<TREND>
+
+Create a "sliding window" average of another data series.
+
+Usage:
+CDEF:smoothed=x,1800,TREND
+
+This will create a half-hour (1800 second) sliding window average of x.  The
+average is essentially computed as shown here:
+
+                 +---!---!---!---!---!---!---!---!--->
+                                                     now
+                       delay     t0
+                 <--------------->
+                         delay       t1
+                     <--------------->  
+                              delay      t2
+                         <--------------->
+
+
+     Value at sample (t0) will be the average between (t0-delay) and  (t0)
+     Value at sample (t1) will be the average between (t1-delay) and  (t1)
+     Value at sample (t2) will be the average between (t2-delay) and  (t2)
+
 =item Special values
 
 B<UNKN>
@@ -130,6 +170,13 @@ set or otherwise the result of vname variable at the previous time
 step. This allows you to do calculations across the data.  This
 function cannot be used in B<VDEF> instructions.
 
+B<COUNT>
+
+Pushes the number 1 if this is the first value of the data set, the 
+number 2 if it is the second, and so on. This special value, allows 
+you to make calculations based on the position of the value within 
+the data set. This function cannot be used in B<VDEF> instructions.
+
 Z<>
 
 =item Time
@@ -194,7 +241,7 @@ 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>
 
@@ -204,7 +251,7 @@ 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>
 
@@ -212,7 +259,7 @@ 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