glitch in "missing" doc?

[Allin C. <cot...@wf...>]

It seems there's a small inaccuracy in the current (5.2.4) help for 
"missing". Here's the relevant part of the text:

<quote>
Gnuplot makes a distinction between missing data and invalid data 
(e.g. "NaN", 1/0.).  For example invalid data causes a gap in a line 
drawn through sequential data points; missing data does not.

Non-numeric characters found in a numeric field will usually be 
interpreted as invalid rather than as a missing data point unless they 
happen to match the `missing` string.
</quote>

In fact it seems that in a data block anything other than "NaN" (on a 
case-insensitive comparison) is treated as "missing" (in the 
operational sense that it does not produce a gap in a line plot), not 
invalid. Here's a little test script:

set term pngcairo
set output 'test.png'
set nokey
plot '-' using 1:2 w lines
2000 1
2001 2
2002 TEST_HERE
2003 2
2004 3
e

The plot is drawn with a line from (2001,2) to 2003,2), and that 
remains the case if I put "?", ".", "NA" or "foo" in place of 
"TEST_HERE". A gap appears only if I substitute "nan" or equivalent.

There's a practical consequence: if I'm in the habit of writing "?" 
for missing values in gnuplot input data, the doc would give me the 
idea that I could toggle "gaps in lines" behavior by inserting or
removing

set datafile missing "?"

With this set I should get no gaps, without it I should get gaps.
But get no gaps regardless.

-- 
Allin Cottrell
Department of Economics
Wake Forest University, NC