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15.2.2.5 Text Properties

string
The character string contained by the text object.
units
May be "normalized" or "graph".
position
The coordinates of the text object.
rotation
The angle of rotation for the displayed text, measured in degrees.
horizontalalignment
May be "left", "center", or "right".
color
The color of the text. See Colors.
fontname
The font used for the text.
fontsize
The size of the font, in points to use.
fontangle
Flag whether the font is italic or normal. Valid values are 'normal', 'italic' and 'oblique'.
fontweight
Flag whether the font is bold, etc. Valid values are 'normal', 'bold', 'demi' or 'light'.
interpreter
Determines how the text is rendered. Valid values are 'none', 'tex' or 'latex'.

All text objects, including titles, labels, legends, and text, include the property 'interpreter', this property determines the manner in which special control sequences in the text are rendered. If the interpreter is set to 'none', then no rendering occurs. At this point the 'latex' option is not implemented and so the 'latex' interpreter also does not interpret the text.

The 'tex' option implements a subset of TeX functionality in the rendering of the text. This allows the insertion of special characters such as Greek or mathematical symbols within the text. The special characters are also inserted with a code starting with the back-slash (\) character, as in the table tab:extended.

In addition, the formatting of the text can be changed within the string with the codes

\bf Bold font
\it Italic font
\sl Oblique Font
\rm Normal font

These are be used in conjunction with the { and } characters to limit the change in the font to part of the string. For example 

     xlabel ('{\bf H} = a {\bf V}')

where the character 'a' will not appear in a bold font. Note that to avoid having Octave interpret the backslash characters in the strings, the strings should be in single quotes.

It is also possible to change the fontname and size within the text

\fontname{fontname} Specify the font to use
\fontsize{size} Specify the size of the font to use

Finally, the superscript and subscripting can be controlled with the '^' and '_' characters. If the '^' or '_' is followed by a { character, then all of the block surrounded by the { } pair is super- or sub-scripted. Without the { } pair, only the character immediately following the '^' or '_' is super- or sub-scripted.

\forall \exists \ni
\cong \Delta \Phi
\Gamma \vartheta \Lambda
\Pi \Theta \Sigma
\varsigma \Omega \Xi
\Psi \perp \alpha
\beta \chi \delta
\epsilon \phi \gamma
\eta \iota \varphi
\kappa \lambda \mu
\nu \o \pi
\theta \rho \sigma
\tau \upsilon \varpi
\omega \xi \psi
\zeta \sim \Upsilon
\prime \leq \infty
\clubsuit \diamondsuit \heartsuit
\spadesuit \leftrightarrow \leftarrow
\uparrow \rightarrow \downarrow
\circ \pm \geq
\times \propto \partial
\bullet \div \neq
\equiv \approx \ldots
\mid \aleph \Im
\Re \wp \otimes
\oplus \oslash \cap
\cup \supset \supseteq
\subset \subseteq \in
\notin \angle \bigrightriangledown
\langle \rangle \nabla
\prod \surd \cdot
\neg \wedge \vee
\Leftrightarrow \Leftarrow \Uparrow
\Rightarrow \Downarrow \diamond
\copyright \lfloor \lceil
\rfloor \rceil \int

Table 15.1: Available special characters in TeX mode

A complete example showing the capabilities of the extended text is 

     x = 0:0.01:3;
     plot(x,erf(x));
     hold on;
     plot(x,x,"r");
     axis([0, 3, 0, 1]);
     text(0.65, 0.6175, strcat('\leftarrow x = {2/\surd\pi',
     ' {\fontsize{16}\int_{\fontsize{8}0}^{\fontsize{8}x}}',
     ' e^{-t^2} dt} = 0.6175'))