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#### 15.2.5 Multiple Plot Windows

You can open multiple plot windows using the `figure` function. For example,

         figure (1);
         fplot (@sin, [-10, 10]);
         figure (2);
         fplot (@cos, [-10, 10]);

creates two figures, with the first displaying a sine wave and the second a cosine wave. Figure numbers must be positive integers.

— Function File: figure (n)
— Function File: figure (n, property, value, ...)

> Set the current plot window to plot window n. If no arguments are specified, the next available window number is chosen.

> Multiple property-value pairs may be specified for the figure, but they must appear in pairs.

#### 15.2.6 Use of `axis`, `line`, and `patch` functions

You can create axes, line, and patch objects directly using the `axes`, `line`, and `patch` functions. These objects become children of the current axes object.

— Function File: axes ()
— Function File: axes (property, value, ...)
— Function File: axes (h)

> Create an axes object and return a handle to it.

— Function File: line ()
— Function File: line (x, y)
— Function File: line (x, y, z)
— Function File: line (x, y, z, property, value, ...)

> Create line object from x and y and insert in current axes object. Return a handle (or vector of handles) to the line objects created.

> Multiple property-value pairs may be specified for the line, but they must appear in pairs.

— Function File: patch ()
— Function File: patch (x, y, c)
— Function File: patch (x, y, z, c)
— Function File: patch (fv)
— Function File: patch ('Faces', f, 'Vertices', v, ...)
— Function File: patch (..., prop, val)
— Function File: patch (h, ...)
— Function File: h = patch (...)

> Create patch object from x and y with color c and insert in the current axes object. Return handle to patch object.

> For a uniform colored patch, c can be given as an RGB vector, scalar value referring to the current colormap, or string value (for example, "r" or "red").

> If passed a structure fv contain the fields "vertices", "faces" and optionally "facevertexcdata", create the patch based on these properties.

— Function File: fill (x, y, c)
— Function File: fill (x1, y1, c1, x2, y2, c2)
— Function File: fill (..., prop, val)
— Function File: fill (h, ...)
— Function File: h = fill (...)

> Create one or more filled patch objects, returning a patch object for each.

— Function File: surface (x, y, z, c)
— Function File: surface (x, y, z)
— Function File: surface (z, c)
— Function File: surface (z)
— Function File: surface (..., prop, val)
— Function File: surface (h, ...)
— Function File: h = surface (...)

> Plot a surface graphic object given matrices x, and y from `meshgrid` and a matrix z corresponding to the x and y coordinates of the surface. If x and y are vectors, then a typical vertex is (x(j), y(i), z(i,j)). Thus, columns of z correspond to different x values and rows of z correspond to different y values. If x and y are missing, they are constructed from size of the matrix z.

> Any additional properties passed are assigned to the surface.

> See also: surf, mesh, patch, line.

#### 15.2.7 Manipulation of plot windows

By default, Octave refreshes the plot window when a prompt is printed, or when waiting for input. The `drawnow` function is used to cause a plot window to be updated.

— Built-in Function: drawnow ()
— Built-in Function: drawnow ("expose")
— Built-in Function: drawnow (term, file, mono, debug_file)

> Update figure windows and their children. The event queue is flushed and any callbacks generated are executed. With the optional argument `"expose"`, only graphic objects are updated and no other events or callbacks are processed. The third calling form of `drawnow` is for debugging and is undocumented.

Only figures that are modified will be updated. The `refresh` function can also be used to force an update of the current figure, even if it is not modified.

— Function File: refresh ()
— Function File: refresh (h)

> Refresh a figure, forcing it to be redrawn. Called without an argument the current figure is redrawn, otherwise the figure pointed to by h is redrawn.

> See also: drawnow.

Normally, high-level plot functions like `plot` or `mesh` call `newplot` to initialize the state of the current axes so that the next plot is drawn in a blank window with default property settings. To have two plots superimposed over one another, use the `hold` function. For example,

         hold on;
         x = -10:0.1:10;
         plot (x, sin (x));
         plot (x, cos (x));
         hold off;

displays sine and cosine waves on the same axes. If the hold state is off, consecutive plotting commands like this will only display the last plot.

— Function File: newplot ()

> Prepare graphics engine to produce a new plot. This function is called at the beginning of all high-level plotting functions. It is not normally required in user programs.

— Command: hold
— Command: hold state
— Function File: hold (hax, ...)

> Toggle or set the 'hold' state of the plotting engine which determines whether new graphic objects are added to the plot or replace the existing objects.

> `hold on`
>   Retain plot data and settings so that subsequent plot commands are displayed on a single graph.
> `hold all`
>   Retain plot line color, line style, data and settings so that subsequent plot commands are displayed on a single graph with the next line color and style.
> `hold off`
>   Clear plot and restore default graphics settings before each new plot command. (default).
> `hold`
>   Toggle the current 'hold' state.

> When given the additional argument hax, the hold state is modified only for the given axis handle.

> To query the current 'hold' state use the `ishold` function.

> See also: ishold, cla, newplot, clf.

— Command: ishold

> Return true if the next plot will be added to the current plot, or false if the plot device will be cleared before drawing the next plot.

> See also: hold.

To clear the current figure, call the `clf` function. To clear the current axis, call the `cla` function. To bring the current figure to the top of the window stack, call the `shg` function. To delete a graphics object, call `delete` on its index. To close the figure window, call the `close` function.

— Function File: clf ()
— Function File: clf ("reset")
— Function File: clf (hfig)
— Function File: clf (hfig, "reset")

> Clear the current figure window. `clf` operates by deleting child graphics objects with visible handles (`handlevisibility` = on). If hfig is specified operate on it instead of the current figure. If the optional argument `"reset"` is specified, all objects including those with hidden handles are deleted.

> See also: cla, close, delete.

— Function File: cla ()
— Function File: cla ("reset")
— Function File: cla (hax)
— Function File: cla (hax, "reset")

> Delete the children of the current axes with visible handles. If hax is specified and is an axes object handle, operate on it instead of the current axes. If the optional argument `"reset"` is specified, also delete the children with hidden handles.

> See also: clf.

— Command: shg

> Show the graph window. Currently, this is the same as executing `drawnow`.

> See also: drawnow, figure.

— Function File: delete (file)
— Function File: delete (handle)

> Delete the named file or graphics handle.

> Deleting graphics objects is the proper way to remove features from a plot without clearing the entire figure.

> See also: clf, cla.

— Command: close
— Command: close (n)
— Command: close all
— Command: close all hidden

> Close figure window(s) by calling the function specified by the `"closerequestfcn"` property for each figure. By default, the function `closereq` is used.

> See also: closereq.

— Function File: closereq ()

> Close the current figure and delete all graphics objects associated with it.

> See also: close, delete.

#### 15.2.8 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 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'))

The result of which can be seen in fig:extendedtext

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