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#### 15.2.7 Use of the `interpreter` Property

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 backslash (\) character, as in the table Table 15.1.

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.

Greek Lowercase Letters
| \alpha | \beta | \gamma
| \delta | \epsilon | \zeta
| \eta | \theta | \vartheta
| \iota | \kappa | \lambda
| \mu | \nu | \xi
| \o | \pi | \varpi
| \rho | \sigma | \varsigma
| \tau | \upsilon | \phi
| \chi | \psi | \omega
Greek Uppercase Letters
| \Gamma | \Delta | \Theta
| \Lambda | \Xi | \Pi
| \Sigma | \Upsilon | \Phi
| \Psi | \Omega |
Misc Symbols Type Ord
| \aleph | \wp | \Re
| \Im | \partial | \infty
| \prime | \nabla | \surd
| \angle | \forall | \exists
| \neg | \clubsuit | \diamondsuit
| \heartsuit | \spadesuit |
“Large” Operators
| \int
Binary Operators
| \pm | \cdot | \times
| \ast | \circ | \bullet
| \div | \cap | \cup
| \vee | \wedge | \oplus
| \otimes | \oslash |
Relations
| \leq | \subset | \subseteq
| \in | \geq | \supset
| \supseteq | \ni | \mid
| \equiv | \sim | \approx
| \cong | \propto | \perp
Arrows
| \leftarrow | \Leftarrow | \rightarrow
| \Rightarrow | \leftrightarrow | \uparrow
| \downarrow |  |
Openings and Closings
| \lfloor | \langle | \lceil
| \rfloor | \rangle | \rceil
Alternate Names
| \neq
Other
| \ldots | \0 | \copyright
| \deg

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'))

The result of which can be seen in Figure 15.7

Figure 15.7: Example of inclusion of text with the TeX interpreter

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