How to build a line with missing data points in gnuplot

Question

Example:

I want to plot the same as above: a line with some missing data points, which means the line is broken.

How can i do this?

Answer 1

It depends on how your data file looks. If you enter an empty space in your data file, it will not connect these neighboring points (this is the easiest way):

consider the following issues:

#datafile 1 2 2 3 4 2 5 3 

and then a script to build it:

  plot 'datafile' u 1:2 w linespoints 

There are other tricks that you can play with missing data: set datafile missing . A good reference for this is the built-in help ( help missing ).

Answer 2

For a single graph, use set datafile missing to specify a character string that means the missing value, and the using $ qualifier to ensure that gnuplot leaves a space in the string for the missing value. Various using qualifiers are described in the gnuplot documentation for set datafile missing .

If the column number is specified as a variable, it is a little more complicated. For example, to build multiple columns of a file, you can specify the column number using a variable:

 do for [i=2:10] { plot 'datafile' using ($1):i with lines } 

However, if we try to use the $ syntax, it does not work:

 do for [i=2:10] { plot 'datafile' using ($1):($i) # ERROR! } 

The solution is to use a column function that also leaves spaces for missing values:

 do for [i=2:10] { plot 'datafile' using ($1):(column(i)) with lines }