MATLAB command contour

The first graphical representation using MATLAB software is that of a two-dimensional contour surface plot of the data from Table 75-1 [2], This Figure 75-3 plot can represent multiple levels of j-axis data (absorbance) by the use of contours and color schemes. The MATLAB commands for generating this image are given in Table 75-2 where A represents the raster data matrix shown in Table 75-1. 

Table 75-2 MATLAB commands for generating a contour plot of data matrix A found in Table 75-1...

Table 75-4 MATLAB commands for generating a 2-D contour plot over a 3-D surface plot...

Script file fig627.m produces the Nichols chart for Example 6.4 when K = 4, as illustrated in Figure 6.27. The command ngrid produces the closed-loop magnitude and phase contours and axis provides user-defined axes. Some versions of MATLAB appear to have problems with the nichols command. 

Note that r locus and r locf ind works for both continuous and discrete systems. The statement squar e provides square axes and so provides a round unit circle. The command zgr id creates a unit circle together with contours of constant natural frequency and damping, within the unit circle. When examp76.m has been run, using r locf ind at the MATLAB prompt allows points on the loci to be selected and values of K identified (see Figure 7.20)... 

The last two codes contain many intricate and useful plotting and contour commands that are self-explanatory when one uses the MATLAB help. .. function for the MAT-LAB graphics commands meshgrid, surface, contour3, xlabel, ylabel, title, colormap, etc. Students should study these graphics commands of MATLAB in order to be learn how to display the easily computed numerical data well. Please refer to MATLAB help. ... 

With MATLAB, you can generate other types of plots, including contour and surfttce plots. You can also control the x- and y-axis scales. For example, the MATLAB s loglog (X, y) uses the base-10 logarithmic scales forx- andy-axes. Notexandy are the variables that you want to plot. The command loglog(X/y) is identical to the plot (x,y), ... 

The Nichols chart in Fig. J.15 provides a graphical display of the closed-loop frequency response characteristics for set-point changes when G is) = Kjn Contours of constant AR l and ql are shown on a plot of ARol vs. OL- In a typical Nichols chart application, ARq and ql are calculated from Gol s) and plotted on the Nichols chart as a series of points. Then AR l and CL are obtained by interpolation. For example, if ARol 1 and ql = -100° at a certain frequency, then interpolation of Fig. J.15 gives ARcl = 0.76 and CL = 50° for the same frequency. The Nichols chart can be generated in the MATLAB Control Toolbox by a single command, nichols. 

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