Question

I have a data file which looks roughly like this

# X  Y   Value
1    1   1.5
1    2   2.5
2    1   NaN
2    2   3.0

I want to create a scatter plot in Gnuplot with crosses at each point and a label with the value beside it.

set datafile missing "NaN"
plot "data.txt" using 1:2:3 with labels left, \
     "data.txt" using 1:2 with points

I would like to see a label with a literal string NaN for the points with an undefined value. Instead no label is printed. Is there a setting to force undefined values to be printed?

I tried this, but still no labels for undefined values:

plot "data.txt" using 1:2:(($3==$3) ? $3 : "NaN") with labels left

It looks like the undefined points are skipped altogether

Answer 1

The following works just fine for me (gnuplot 4.4 and gnuplot 4.6):

plot 'data.txt' u 1:2:3 w labels left,\
     'data.txt' u 1:2 w points

In fact, copy/pasting your original code works for me as well:

set datafile missing "NaN"
plot "data.txt" using 1:2:3 with labels left, \
     "data.txt" using 1:2 with points

Perhaps you’re not noticing the labels because they are almost off the screen?

set xrange [0:3]
set yrange [0:3]

helps them to be a little easier to see…