gnuplot documentation

70 SET-SHOW gnuplot 4.3 95
70.14 Datafile
The set datafile command options control interpretation of fields read from input data files by the
plot, splot, and fit commands. Four such options are currently implemented.
70.14.1 Set datafile fortran
The set datafile fortran command enables a special check for values in the input file expressed as
Fortran D or Q constants. This extra check slows down the input process, and should only be selected
if you do in fact have datafiles containing Fortran D or Q constants. The option can be disabled again
using unset datafile fortran.
70.14.2 Set datafile missing
The set datafile missing command allows you to tell gnuplot what character string is used in a data
file to denote missing data. Exactly how this missing value will be treated depends on the using specifier
of the plot or splot command.
Syntax:
set datafile missing {""}
show datafile missing
unset datafile
Example:
# Ignore entries containing IEEE NaN ("Not a Number") code
set datafile missing "NaN"
Example:
set datafile missing "?"
set style data lines
plot ’-’
1 10
2 20
3 ?
4 40
5 50
e
plot ’-’ using 1:2
1 10
2 20
3 ?
4 40
5 50
e
plot ’-’ using 1:($2)
1 10
2 20
3 ?
4 40
5 50
e
The first plot will recognize only the first datum in the "3 ?" line. It will use the single-datum-on-a-line
convention that the line number is "x" and the datum is "y", so the point will be plotted (in this case
erroneously) at (2,3).
The second plot will correctly ignore the middle line. The plotted line will connect the points at (2,20)
and (4,40).