COMMAND NAME:	fraction

TYPE:		Data selection

SYNTAX:	  e.g.	"fraction > 8"
	    or	"fraction <= 60%"

DESCRIPTION:

Sets the fraction of the data processed for this scan which
will pass the filtering functions applied in read, edit, and
plot.  The syntax is quite forgiving.  The requirements are
that there be an inequality operator, possibly followed by
an equals sign, followed by a sensible number, possibly followed
by a percent sign.  If the percent sign is missing, the number
is interpreted as tenths of the scheduled data, instead of a 
percentage.  Spaces are irrelevant.

If "fraction" is typed with no arguments, or with
just "0" as an argument, all restrictions on the fraction of
data processed are removed.

Note that this filter option operates on the value of the last
digit in the ESDESP field of the A-file format, which is placed
there by FRNGE or fourfit.  Before the implementation of baseline-
dependent scan lengths in the schedule files, this number was 
unreliable.  Also, being only a single digit, this quantity is 
only accurate to the nearest 10%, so more precise values entered 
with the fraction command are rounded off.