SMOOTH = expr;                   Enable or disable smoothing

Value of 'expr' determines whether smoothing is performed for
subsequent processing as follows:
         0 => no smoothing
     not 0 => enable smoothing

Use predefined constants ON and OFF to enable or disable smoothing.

With smoothing enabled, all data points in a file  between
successive step times are averaged.  Additionally, the time tags
associated with those data points are averaged and a value is not
output until the average time tag is beyond the current step time. 
Hence the value plotted/ printed/ etc. is the average value of all
data points surrounding each step time.  This mechanism helps
reduce phase distortion caused by averaging during monotonic
sections of a trace.
+
Smoothing an already smooth function will distort it.

Smoothing is only effective when there is a surplus of data points;
that is, when there are at least twice as many data points as
points to be plotted/processed (determined by STEP and DUR).
