More on Plots. Dmitry Adamskiy 30 Nov 2011

Transcription

1 More on Plots Dmitry Adamskiy 3 Nov 211 1

2 plot3 (1) Recall that plot(x,y), plots vector Y versus vector X. plot3(x,y,z), where x, y and z are three vectors of the same length, plots a line in 3-space through the points whose coordinates are the elements of x, y and z plot3() is the 3D analogue of plot() 2

3 plot3 (2) plot3(x,y,z), where x, y and z are three matrices of the same size, plots several lines obtained from the columns of x, y and z. Various line types, plot symbols and colours may be obtained with plot3(x,y,z,s) where s is a character string made from the characters listed under the plot command. 3

4 Example X = : pi/1 : 2*pi; Y = sin(x); Z = ones(1,21); plot3(x,y,z) grid on xlabel('x') ylabel('y') zlabel('z') 4

5 2 1.5 Z Y X 4 6 8

6 3D Plot Manipulation Icons at the top of the figure window: Zoom In / Zoom Out (plus / minus) Pan (a hand) Rotate 3D (an arrow going in a circle) 6

7 bar (1) bar(y) draws a bar graph: if Y is a vector, it draws one bar for each element in Y. If Y is a matrix, bar groups the bars produced by the elements in each row in different subplots. bar(x,y) draws a bar for each element in Y at locations specified in X, where X is a vector defining the x-axis intervals for the vertical bars. 7

8 Example (1) M = magic(4); subplot(3,1,1); bar(m) 8

9 bar (2) bar(x,y,width) or bar(y,width) specifies the width of the bars. Values of WIDTH > 1, produce overlapped bars. The default value is WIDTH=.8 bar(...,'grouped') produces the default vertical grouped bar chart. bar(...,'stacked') produces a vertical stacked bar chart. 9

10 Example (2) subplot(3,1,2) bar(m, stacked ) subplot(3,1,3) bar(m,.5, grouped ) 1

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12 colormap (1) The colormap is an object which defines the colours in graphs and plots A colormap is an m-by-3 matrix of real numbers between. and 1.. Each row is an RGB vector that defines one colour. The kth row of the colormap defines the kth colour, where map(k,:) = [r(k) g(k) b(k)]) specifies the intensity of red, green, and blue. 12

13 colormap (2) colormap(map) sets the colormap to the matrix map. If any values in map are outside the interval [ 1], MATLAB returns the error `Colormap must have values in [,1] Example: colormap([ ; 1 ; 1 1 ; 1 ]) Note: the colours changes without us redrawing the plot 13

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15 Matlab Supported Colormaps MATLAB has a number of predefined colormaps To get a list of all the MATLAB supported colormaps type in help graph3d and look at the list under the Color maps heading For example, autumn varies smoothly from red, through orange, to yellow. Try colormap(autumn) 15

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17 bar3 bar3 is a 3D bar graph Try >> M = magic(4); >> subplot(2,1,1); bar(m) >> subplot(2,1,2); bar3(m) 17

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19 pie (1) pie(x) draws a pie plot of the data in the vector X. If sum(x) <= 1, the values in X directly specify the area of the pie slices. Only a partial pie will be drawn if sum (X) < 1. Otherwise the values in X are normalised via X/sum(X) to determine the area of each slice of pie. Example: [2 3 5] are plotted as [.2.3.5] 19

20 pie (2) pie(x,explode) is used to specify slices that should be pulled out from the pie. The vector EXPLODE must be the same size as X. The slices where EXPLODE is non-zero will be pulled out. pie(...,labels) is used to label each pie slice with cell array LABELS. LABELS must be the same size as X and can only contain strings. 2

21 Example >> subplot(2,2,1) >> pie([ ]) >> subplot(2,2,2) >> pie([.2.5.3]) >> subplot(2,2,3) >> pie([.5.2],{ North, South }) >> subplot(2,2,4) >> pie([ ],[1 ]) 21

22 2% 5% 15% 2% 3% 25% 35% 5% 17% 33% North 22% South 28% 22

23 pie3 pie3(x) draws a 3-D pie plot of the data in the vector X. Try >> figure >> pie3([ ],[ 1 1 ], {'North','South','East','West'}) >> colormap(summer) 23

24 West North South East 24

25 fill fill(x,y,c) fills the 2-D polygon defined by vectors X and Y with the color specified by C. The vertices of the polygon are specified by pairs of components of X and Y. If necessary, the polygon is closed by connecting the last vertex to the first. C: a single character string chosen from the list 'r','g','b','c','m','y','w','k or an RGB row vector triple [r g b] 25

26 Example >> figure >> fill([ ],[ ],'c') >> axis([ 5 4]) 26

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28 compass compass(u,v) draws a graph that displays the vectors with components (U,V) as arrows emanating from the origin. Example >> figure >> compass([1 2 3], [1 3 ]) 28

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30 surf surf draws a shaded surface plot in 3D surf(x,y,z), where X, Y, Z are matrices of the same dimensions creates a surface plot with vertices in (X(i, j), Y(i,j), Z(i,j)) if X and Y are vectors, length(x) = n and length(y) = m, where [m,n] = size(z); and vertices are in (X(j), Y(i), Z(i,j)) surf(z): if X and Y are omitted, MATLAB uses X = 1:n and Y = 1:m, where [m,n] = size(z) colour is proportional to surface height (Z) 3

31 Example The following code plots the function z(x, y) = sin(x) + cos(y) >> x = : pi/1 : 4*pi; >> y = : pi/1 : 4*pi; >> z = sin(repmat(x, 41, 1)) + cos(repmat(y, 1, 41)); >> figure >> surf (x, y, z); Why do we need to use repmat? 31

32 mesh mesh draws a 3D mesh plot - wireframe surfaces (similar to surf but without faces) The use is similar to surf Try >> figure >> mesh (x, y, z) 32

33 sphere sphere(n) draws a unit sphere consisting of n-by-n faces sphere without arguments generates a sphere consisting of 2-by-2 faces [X,Y,Z] = sphere(n) returns the coordinates of a sphere in three matrices that are (n+1)-by-(n+1) in size. You can later draw the sphere with surf(x,y,z) or mesh(x,y,z). 33

34 Example >> figure >> [X,Y,Z] = sphere(1); >> subplot(2,2,1); surf(x,y,z) >> subplot(2,2,2); mesh(x,y,z) >> subplot(2,2,3); sphere(5) >> subplot(2,2,4); sphere 34

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36 Images image(z) and imagesc(z) plot matrix Z as a coloured pattern. Each element of Z specifies the color of a rectangular segment in the image. image(x,y,z), where x and y are vectors, specifies the range of the x- and y- axis labels but produces the same image as image(z) imagesc scales the colour automatically to look nice the command colorbar adds a scale at the side of the image colormap changes the colours used. 36

37 Example >> x = : pi/1 : 4*pi; >> y = : pi/1 : 4*pi; >> z = sin(repmat(x, 41, 1)) + cos(repmat(y, 1, 41)); >> figure >> imagesc (x, y, z); >> colorbar 37

38 3-D and 2-D Graphics For a list of 3-D graphical functions type in help graph3d For a list of 2-D graphical functions type in help graph2d 38

39 Plotting from the Workspace Browser Some plots are implemented in a plot selector in the Workspace browser and can be drawn at a mouse click Choose a variable in the Workspace browser and choose the plot type in a plot selector Click on More Plots and browse through plot categories and types in a Plot Catalog You can also select several variables at a time and plot them 39

40 4 Graphics Handles

41 Graphics Handles All figures, subplots, axes, lines on plots etc have a handle which you use to tell Matlab which part of a figure you want to edit. Most of the time the handles are completely invisible to the user - you don t need to know or care about them, but there are a couple which are useful 41

42 gcf gcf is the handle to the current figure get(gcf) shows all the properties of the current figure set(gcf, property_name, property_value) changes property property_name to value property_value Example: set(gcf,'position',[5,5,6,8]) puts the current figure 5 pixels above and 5 pixels to the left of the bottom left hand corner of the screen, and make the figure 6 pixels wide and 8 pixels high. 42

43 gca gca is the handle to the current axis get(gca) shows you all the properties you can edit set(gcf, property_name, property_value) changes property property_name to value property_value Example: set(gca,'xtick',1:4','xticklabel', {'cat','dog','car','boat'}) This gives the current axis four tick marks at numbers 1 to 4, and puts the words 'cat', 'dog' etc on each tick mark. 43

44 Line Handles Line handles are obtained by giving a plotting function an output. h = plot(1:1, rand(1,1)) h is now the handle to your line You can use h to do things like change the colour or width of the line set(h,'linewidth',3) 44

45 Acknowledgements In the preparation of the material for this handout use has been made of the following sources: MATLAB 7 manuals 45