Re: [Gnuplot-info] plot by filtering some lines

[William Xu <wil...@gm...>]

Hans-Bernhard Bröker <HBB...@t-...> writes:

> No.  1/0 is an invalid coordinate.  But that's still not the same as the 
> total absense of an entire datapoint.  An input line with invalid 
> coordinates works like an empty input line, a.k.a. "blank record".  See 
> "help datafile" about the effect of blank records.

Okay, i found the "blank record": 

,----
| In datafiles, blank records (records with no characters other than
| blanks and a newline and/or carriage return) are significant -- pairs of
| blank records separate indexes (see plot datafile index (p. [*])). Data
| separated by double blank records are treated as if they were in
| separate data files.
`----

It simply says "blank"(whitespaces, newline, etc) records are "blank
records", but it doesn't say that infinite/undefined coordinates are
also "blank records". 

In "using" section, I also found no hint indicating "blank records",
(which i quoted previously)

,----
| One trick is to use the ternary ?: operator to filter data:
| 
| 
|      plot 'file' using 1:($3>10 ? $2 : 1/0)
| 
| 
| which plots the datum in column two against that in column one provided
| the datum in column three exceeds ten. 1/0 is undefined; gnuplot quietly
| ignores undefined points, so unsuitable points are suppressed. 
`----

Am I missing something?

-- 
William