The final plotting command, plt, plots text rather than geometrical
Optional keywords determine the font, size, color, and orientation of
the characters, and the precise meaning of the coordinates x and y --
what coordinate system they are given in, and how the text is justified
relative to the given point.
Unlike the other plotting primitives, by default the (x,y) coordinates
in the plt command do not refer to the same (x,y) scales as your data.
Instead, they are so-called normalized device coordinates, which are
keyed to the sheet of paper, should you print a hardcopy of your
picture. To make (x,y) refer to the so-called world coordinates of
your data (what planet is your data from?), you must use the tosys=1
keyword. If you do locate text in your world coordinate system, only
its position will follow your data as you zoom and pan through it;
don't expect text size to grow as you zoom in, or your characters to
become hideously distorted when you switch to log axis scaling.
Text may be rotated by multiples of 90 degrees by means of the
orient= keyword. Arbitrary rotation angles are not supported, and
the speed that rotated text is rendered on your screen may be
dramatically slower than ordinary unrotated text.
You can get superscripts, subscripts, and symbol characters by means
of escape sequences in the text. Yorick is not a typesetting program,
and these features will not be the highest possible quality. Neither
will what you see on the screen be absolutely identical to your
printed hardcopy (that is never true, actually, but superscripts and
subscripts are noticeably different). With those caveats, the escape
feature is still quite useful.
To get a symbol character (assuming you are a font other than symbol),
precede that character by an exclamation point -- for example,
"!p" will be plotted as the Greek letter pi. There are four
exceptions: "!!", "!^", and "!_" escape to the
non-symbol characters exclamation point, caret, and underscore,
respectively. And "!]" escapes to caret in the symbol font, which
is the symbol for perpendicular. The exclamation point, underscore, and
right bracket characters are themselves in the symbol font, and
shouldn't be necessary as escaped symbols. If the last character
in the text is an exclamation point, it has no special meaning; you
do not need to escape a trailing exclamation point.
Caret "^" introduces superscripts and underscore "_"
introduces subscripts. There are no multiple levels of superscripting;
every character in the text string is either ordinary, a superscript, or
a subscript. A caret switches from ordinary or subscript characters to
superscript, or from superscript to ordinary. An underscore switches
from ordinary or superscript characters to subscript, or from subscript
back to ordinary.
If the text has multiple lines (separated by newline "\n"
characters), plt will plot it in multiple lines, with each line
justified according to the justify= keyword, and with the vertical
justification applied to the whole block. You should always use the
appropriate text justification, since the size of the text varies
from one output device to another -- the size of the text you see on
your screen is only approximately the size in hardcopy. In multiline
text, the superscript and subscript state is reset to ordinary at
the beginning of each line.
Here is an example of escape sequences:
text = "The area of a circle is !pr^2\n"+
"Einstein's field equations are G_!s!n_=8!pT_!s!n";
plt, text, .4,.7,justify="CH";