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Unformatted text preview: CSC 113: Saving Plots and Graphics in Matlab This document covers the basics of saving a figure created in MATLAB, so that it may be used in some other setting, such as a web page, written report, or overhead presentation. First, let’s create a figure. The following script will plot the fourth- and fifth-order Chebyshev polynomials for a range of input values: % % Simple plot script % % Create range of x values and their squares: % xx = linspace(-1.1,1.1,200); xx2 = xx . * xx; % % Chevyshev polynomials of orders 4 and 5: % % T ¯ 4(x) = 8 xˆ4 - 8 xˆ2 + 1 % T ¯ 5(x) = 16 xˆ5 - 20 xˆ3 + 5 x % T4 = (8 * xx2 - 8) . * xx2 + 1; T5 = ((16 * xx2 -20) . * xx2 + 5) . * xx; figure(1); plot(xx,T4,’linewidth’,2); axis([-1.1 1.1 -5 5]); hold on plot(xx,T5,’r’,’linewidth’,2); % % Draw a dashed square box, % to highlight the equi-ripple region of the % Chebyshev polynomials: % xpath = [-1 -1 1 1 -1]; ypath = [-1 1 1 -1 -1]; plot(xpath,ypath,’-.’); hold off xlabel(’Input argument’); ylabel(’Function value’); legend(’T ¯ 4(x)’, ’T ¯ 5(x)’,’Location’,’SouthEast’); This should bring up a figure window as in figure 1 . One is tempted to use the “File → Save” menu item; this creates a figure file with the “.fig” extension that is useful for opening the figure in a later MATLAB session. Unfortunately, the *.fig format is only readable by MATLAB, so other programs can’t use it. 1 Figure 1: Figure window produced from the example script. One approach to saving the figure is to use any screen capture program, to perform a “screen dump” of the figure window into a graphic file. (This is how figure 1 was obtained.) The resulting image quality, however, is limited by the screen resolution, and likewise includes other elements (such as the tool bars and window decorations) which distract from the plot itself. Fortunately, MATLAB provides the print command to save the contents of a plotting window as a graphic file. (The command name “print” is a hangover from the early days before graphic computer terminals, when a plot was obtained by sending data points to a line printer.) We’ll examine the following commands: >> print -dpng figplot.png >> print -djpeg figplot.jpg >> print -dtiff figplot.tiff >> print -depsc2 figplot.eps This will create four files, each a different format. (Only one of these commands will be necessary in practice, depending on the desired image format.) The different formats are reviewed in turn: Portable Network Graphics (.png) The “-dpng ” option after the print command tells MATLAB to use the png driver, and name...
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- Fall '10
- Portable Network Graphics, Portable Document Format, image format