1.11 Enhanced text mode

Many terminal types support an enhanced text mode in which additional formatting information is embedded in the text string. For example, "x^2" will write x-squared as we are used to seeing it, with a superscript 2. This mode is normally selected when you set the terminal, e.g. "set term png enhanced", but may also be toggled afterward using "set termoption enhanced", or by marking individual strings as in "set label ’x_2’ noenhanced".

 Control      Examples        Explanation
  ^           a^x             superscript
  _           a_x             subscript
  @           @x or a@^b_{cd} phantom box (occupies no width)
  &           &{space}        inserts space of specified length
  ~           ~a{.8-}         overprints '-' on 'a', raised by .8
                              times the current fontsize

Braces can be used to place multiple-character text where a single character is expected (e.g., 2^{10}). To change the font and/or size, use the full form: {/[fontname][=fontsize | *fontscale] text}. Thus {/Symbol=20 G} is a 20 pt GAMMA and {/*0.75 K} is a K at three-quarters of whatever fontsize is currently in effect. (The ’/’ character MUST be the first character after the ’{’.)

The phantom box is useful for a@^b_c to align superscripts and subscripts but does not work well for overwriting an accent on a letter. For the latter, it is much better to use an encoding (e.g. iso_8859_1 or utf8) that contains a large variety of letters with accents or other diacritical marks. See encoding. Since the box is non-spacing, it is sensible to put the shorter of the subscript or superscript in the box (that is, after the @).

Space equal in length to a string can be inserted using the ’&’ character. Thus

        'abc&{def}ghi'

would produce

        'abc   ghi'.

The ’~’ character causes the next character or bracketed text to be overprinted by the following character or bracketed text. The second text will be horizontally centered on the first. Thus ’~a/’ will result in an ’a’ with a slash through it. You can also shift the second text vertically by preceding the second text with a number, which will define the fraction of the current fontsize by which the text will be raised or lowered. In this case the number and text must be enclosed in brackets because more than one character is necessary. If the overprinted text begins with a number, put a space between the vertical offset and the text (’~{abc}{.5 000}’); otherwise no space is needed (’~{abc}{.5—}’). You can change the font for one or both strings (’~a{.5 /*.2 o}’—an ’a’ with a one-fifth-size ’o’ on top—and the space between the number and the slash is necessary), but you can’t change it after the beginning of the string. Neither can you use any other special syntax within either string. You can, of course, use control characters by escaping them (see below), such as ’~a{\^}’

You can access special symbols numerically by specifying \character-code (in octal), e.g., {/Symbol \245} is the symbol for infinity. This does not work for multibyte encodings like UTF-8, however. In a UTF-8 environment, you should be able to enter multibyte sequences implicitly by typing or otherwise selecting the character you want.

You can escape control characters using \, e.g., \\, \{, and so on.

But be aware that strings in double-quotes are parsed differently than those enclosed in single-quotes. The major difference is that backslashes may need to be doubled when in double-quoted strings.

Examples (these are hard to describe in words—try them!):

      set xlabel 'Time (10^6 {/Symbol m}s)'
      set title '{/Symbol=18 \\362@_{/=9.6 0}^{/=12 x}} \\
                 {/Helvetica e^{-{/Symbol m}^2/2} d}{/Symbol m}'

The file "ps_guide.ps" in the /docs/psdoc subdirectory of the gnuplot source distribution contains more examples of the enhanced syntax.