Matlab Chapter6.pdf

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1.6.1 Setting Axis Limits By default, MATLAB finds the maxima and minima of the data and chooses the axis limits to span this range. The axis command enables you to specify your own limits: ≫ axis([xmin xmax ymin ymax]) or for three-dimensional graphs, ≫ axis([xmin xmax ymin ymax zmin zmax]) Use the command ≫ axis auto to reenable MATLAB automatic limit selection. 1.6.2 Setting the Axis Aspect Ratio The axis command also enables you to specify a number of predefined modes. For example, ≫ axis square makes the x-axis and y-axis the same length. ≫ axis equal makes the individual tick mark increments on the x-axes and y-axes the same length. This means ≫ plot(exp(i ∗ [0 : pi/10 : 2 ∗ pi])) followed by either axis square or axis equal turns the oval into a proper circle: ≫ axis auto normal returns the axis scaling to its default automatic mode. 1.6.3 Setting Axis Visibility You can use the axis command to make the axis visible or invisible. ≫ axis on makes the axes visible. This is the default. ≫ axis off makes the axes invisible. 1.6.4 Setting Grid Lines The grid command toggles grid lines on and off. The statement ≫ grid on turns the grid lines on, and ≫ grid off turns them back off again. For More Information See the axis and axes reference pages and “Axes Properties” in [1]. 1.7 Adding Axis Labels and Titles The xlabel( ), ylabel( ), and zlabel( ) commands add x-, y-, and z-axis labels. The title(text) command adds a text at the top of the figure and the text function inserts text anywhere in the figure. You can produce mathematical symbols using LaTeX notation in the text string, as the following example illustrates: 4
Example 1.4 The characters \ pi create the symbol π. Example 1.5 ≫ xlabel( ′ x = 0 : 2\pi ′ ) ≫ ylabel( ′ Sine of x ′ ) ≫ title( ′ Plot of the Sine Function’,’FontSize ′ , 12) ≫ t = −pi : pi/100 : pi; ≫ y = sin(t); ≫ plot(t, y) ≫ axis([−pi pi − 1 1]) ≫ xlabel( ′ −\pi ≤ t ≤ \pi ′ ) ≫ ylabel( ′ sin(t) ′ ) ≫ title(’Graph of the sine function’) ≫ text(1, −1/3, ′ Notetheoddsymmetry. ′ ) You can also set these options interactively. Note that the location of the text string is defined in axes units (i.e., the same units as the data). Remark 1.2 Graphs may be labeled with the following statements: ≫ gtext(text) writes a string (text) in the graph window. gtext puts a cross-hair in the graph window and waits for a mouse button or keyboard key to be pressed. The cross-hair can be positioned with the mouse or the arrow keys. For example, ≫ gtext(Xmarksthespot) Text may also be placed on a graph interactively with Tools click Edit Plot from the figure window. ≫ text(x, y, text) writes text in the graphics window at the point specified by x and y. If x and y are vectors, the text is written at each point. If the text is an indexed list, successive points are labeled with corresponding rows of the text. ≫ title(text) 1.8 Figure Windows Graphing functions automatically open a new figure window if there are no figure windows already on the screen. If a figure window exists, MATLAB uses that window for graphics output. If there are multiple figure windows open, MATLAB targets the one that is designated the “current figure” (the last figure used or clicked in). To make an existing figure window the current figure, you can click the mouse while the pointer is in that window or you can type ≫ figure(n) where n is the number in the figure title bar. The results of subsequent graphics commands are displayed in this window. ≫ x = 0 : pi/100 : 2 ∗ pi; ≫ y = sin(x); ≫ y2 = sin(x − .25); ≫ y3 = sin(x − .5); ≫ plot(x, y) ≫ plot(x, y2) ≫ plot(x, y3) 5
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Page 3: 1.4 Adding Plots to an Existing Gra
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