By default each plot is listed in the key by the corresponding function or file name. You can give an explicit plot title instead using the title option.
Syntax:
title <text> | notitle [<ignored text>] title columnheader | title columnheader(N)
where <text> is a quoted string or an expression that evaluates to a string. The quotes will not be shown in the key.
There is also an option that will interpret the first entry in a column of input data (i.e. the column header) as a text field, and use it as the key title. See `datastrings`. This can be made the default by specifying columnhead.
The line title and sample can be omitted from the key by using the keyword `notitle`. A null title (`title ”`) is equivalent to `notitle`. If only the sample is wanted, use one or more blanks (`title ' '`). If `notitle` is followed by a string this string is ignored.
If `key autotitles` is set (which is the default) and neither title nor `notitle` are specified the line title is the function name or the file name as it appears on the `plot` command. If it is a file name, any datafile modifiers specified will be included in the default title.
The layout of the key itself (position, title justification, etc.) can be controlled by `set key`. Please see `set key` for details.
Examples:
This plots y=x with the title 'x':
plot x
This plots x squared with title "x^2" and file "data.1" with title "measured data":
plot x**2 title "x^2", 'data.1' t "measured data"
This puts an untitled circular border around a polar graph:
set polar; plot my_function(t), 1 notitle
Plot multiple columns of data, each of which contains its own title in the file
plot for [i=1:4] 'data' using i title columnhead