key autotitle

set key autotitle causes each plot to be identified in the key by the name of the data file or function used in the plot command. This is the default. set key noautotitle disables the automatic generation of plot titles. The command set key autotitle columnheader causes the first entry in each column of input data to be interpreted as a text string and used as a title for the corresponding plot. If the quantity being plotted is a function of data from several columns, gnuplot may be confused as to which column to draw the title from. In this case it is necessary to specify the column explicitly in the plot command, e.g.

      plot "datafile" using (($2+$3)/$4) title columnhead(3) with lines

Note: The effect of set key autotitle columnheader, treatment of the first line in a data file as column headers rather than data applies even if the key is disabled by unset key. It also applies to stats and fit commands even though they generate no key. If you want the first line of data to be treated as column headers but _not_ to use them for plot titles, use set datafile columnheaders.

In all cases an explicit title or notitle keyword in the plot command itself will override the default from set key autotitle.