Lecture note Data visualization - Chapter 24

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The main contents of the chapter consist of the following: Plots with more than one line, plots of complex arrays, line, color and mark style, axis scaling and annotating plots, subplots, polar plots, logarithmic plots, bar graphs and pie charts, histograms, X-Y graphs with two Y-axes.

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Nội dung Text: Lecture note Data visualization - Chapter 24

Lecture 24
Recap Plots with More than one Line Plots of Complex Arrays Line, Color and Mark Style Axis Scaling and Annotating Plots Subplots Polar Plots Logarithmic Plots Bar Graphs and Pie Charts
Function Plots
Three Dimensional Line Plots The plot3 function is similar to the plot function, except that it accepts data in three dimensions Instead of just providing x and y vectors, the user must also provide a z vector These ordered triples are then plotted in threespace and connected with straight lines For example: clear, clc x = linspace(0,10*pi,1000); y = cos(x);
Surface Plots Surface plots allow to represent data as a surface Two types of surface plots Mesh plots Surf plots
Mesh Plots There are several ways to use mesh plots They can be used to good effect with a single two dimensional mxn matrix In this application, the value in the matrix represents the z value in the plot The x and y values are based on the matrix dimensions Take, for example, the following very simple matrix: z = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10; 2, 4, 6, 8, 10, 12, 14, 16, 18, 20; 3, 4, 5, 6, 7, 8, 9, 10, 11, 12];
Explanation of Graph The graph is a “mesh” created by connecting the points defined in z into a rectilinear grid Notice that the x axis goes from 0 to 10 and y goes from 1 to 3 The matrix index numbers were used for the axis values
Mesh Plots Continued…. The mesh function can also be used with three arguments: mesh(x,y,z) In this case, x is a list of x coordinates, y is a list of y coordinates, and z is a list of z coordinates. x = linspace(1,50,10) y = linspace(500,1000,3) z = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10; 2, 4, 6, 8, 10, 12, 14, 16, 18, 20; 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
Surf Plots Surf plots are similar to mesh plots, but surf creates a threedimensional colored surface instead of a mesh The colors vary with the value of z The surf command takes the same input as mesh : either a single input— For example: surf(z) , in which case it uses the row and column indices as x – and y coordinates—or three matrices The command surf(x,y,z)
Continued…. The shading scheme for surface plots is controlled with the shading command The default (shown in previous slide) is “faceted.” Interpolated shading can create interesting effects The plot(in next slide) is created by adding  shading interp to the previous list of commands
Continued…. Flat shading without the grid is generated when shading flat is used
Continued…. The color scheme used in surface plots can be controlled with the colormap function For example: colormap(gray) forces a grayscale representation for surface plots This may be appropriate if you’ll be making blackand white copies of your plots Other available colormaps are autumn bone hot spring colorcube hsv
Example A more complicated surface can be created by calculating the values of Z : x= [2:0.2:2]; y= [2:0.2:2]; [X,Y] = meshgrid(x,y); Z = X.*exp(X.^2 Y.^2); In the preceding code, the meshgrid function is used to create the twodimensional matrices X and Y from the onedimensional vectors x and y The values in Z are then calculated