new operand on rrdgraph CDEFs: PREV(xxxx) -- Gonzalo Augusto Arana Tagle <garana...

[rrdtool.git] / doc / rrdgraph_rpn.src

diff --git a/doc/rrdgraph_rpn.src b/doc/rrdgraph_rpn.src
index 8b5d49b..a8c4b11 100644 (file)
--- a/doc/rrdgraph_rpn.src
+++ b/doc/rrdgraph_rpn.src
@@ -123,6 +123,13 @@ set or otherwise the result of this B<CDEF> at the previous time
 step. This allows you to do calculations across the data.  This
 function cannot be used in B<VDEF> instructions.
 
+B<PREV(vname)>
+
+Pushes an I<unknown> value if this is the first value of a data
+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.
+
 Z<>
 
 =item Time