Sorry, just noticed something. The statement in the doc, "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" is borne out if I substitute
plot '-' using 1:($2) w lines
for
plot '-' using 1:2 w lines
The doc further states, "Old gnuplot versions handled NaN differently
depending of the form of the `using` clause", but it doesn't mention
that the form of the `using` clause matters currently too.
Allin Cottrell
On Sun, 12 Aug 2018, Allin Cottrell wrote:
> 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.
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