Example: C<CDEF:x=a,b,c,d,4,AVG>
-B<TREND>
+B<TREND, TRENDNAN>
Create a "sliding window" average of another data series.
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)
+TRENDNAN is - in contrast to TREND - NAN-safe. If you use TREND and one
+source value is NAN the complete sliding window is affected. The TRENDNAN
+operation ignores all NAN-values in a sliding window and computes the
+average of the remaining values.
+
+
=item Special values
B<UNKN>