INC151 Electrical Engineering Software Practice. MATLAB Graphics. Dr.Wanchak Lenwari :Control System and Instrumentation Engineering, KMUTT 1

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1 INC151 Electrical Engineering Software Practice MATLAB Graphics Dr.Wanchak Lenwari :Control System and Instrumentation Engineering, KMUTT 1

2 Graphical display is one of MATLAB s greatest strengths and most complicated subjects. The basics are quite simple, but you also get complete control over practically every aspect of each graph, and with that power comes complexity. Dr.Wanchak Lenwari :Control System and Instrumentation Engineering, KMUTT 2

3 Plot Types D Plot 3-D Plot MATLAB has many functions and commands that can be used to create various types of plots. Dr.Wanchak Lenwari :Control System and Instrumentation Engineering, KMUTT 3

4 2-D D Plot The very basic 2-D plot command is plot(x,y) where x and y are vectors (both one dimension array). Both vectors must have the same number of elements. e.g. >>x=linspace(0,2*pi,50); >>y=sin(x); >>plot(x,y) Once the plot command is executed, the Figure Window opens with the following plot. Dr.Wanchak Lenwari :Control System and Instrumentation Engineering, KMUTT 4

5 2-D D Plot Dr.Wanchak Lenwari :Control System and Instrumentation Engineering, KMUTT 5

6 2-D D Plot y-axis label sin(x) My first plot Plot Title Q1. Use help in matlab i.e. help plot and put the title, x-axis label and y-axis label as shown in the figure. (10 mins) radian x-axis label Dr.Wanchak Lenwari :Control System and Instrumentation Engineering, KMUTT 6

7 2-D D Plot Q2. Use help in matlab i.e. help plot and change the line colour to red as shown (5 mins) Dr.Wanchak Lenwari :Control System and Instrumentation Engineering, KMUTT 7

8 2-D D Plot 1 Plot title My first plot Legend data1 0.8 y axis label Text Tick-mark 0.2 Text can place everywhere in the graph sin(x) Data marker x Grid radian x axis label Tick-mark label Dr.Wanchak Lenwari :Control System and Instrumentation Engineering, KMUTT 8

9 Line Specifiers Line specifiers can be added in the plot command to: Specify the style of the line. Specify the color of the line. Specify the type of the markers (if markers are desired). plot(x,y, line specifiers ) Dr.Wanchak Lenwari :Control System and Instrumentation Engineering, KMUTT 9

10 Line Specifiers Line Specifier Line Specifier Marker Specifier Style Color Type Solid - red r plus sign + dotted : green g circle o dashed -- blue b asterisk * dash-dot -. Cyan c point. magenta m square s yellow y diamond d black k cross x white w i.e. >>plot(x,y,'-.or') % plots y versus x using a dashdot line (-.), places circular markers (o) at the data points, and colors both line and marker red (r). Dr.Wanchak Lenwari :Control System and Instrumentation Engineering, KMUTT 10

11 Exercise 1 One student has the GPA showing in the table below. Year GPA Plot the student s GPA(in y-axis) against academic year(in x- axis). The line is solid green colour and the points are marked with asterisk. (10 mins) Dr.Wanchak Lenwari :Control System and Instrumentation Engineering, KMUTT 11

12 Plot Labeling In order to make a better plotting, do the following commands.] Title-title('The changing in student s GPA') Xlabel-xlabel('Academic Year') Ylabel-ylabel('GPA') Grid grid on, grid off Legend- legend('gpa') Text- text(x,y,'string') adds the text in the quotes to location (X,Y). i.e. text(2546,3.5, test') %text(2548,3.5,'\leftarrow GPA') Gtext-gtext('GPA') % wait for a mouse to be positioned Ginput-ginput % Graphical input from mouse+return key Dr.Wanchak Lenwari :Control System and Instrumentation Engineering, KMUTT 12

13 Multiple Plots e.g. plot 2 data in one figure >>x=linspace(0,2*pi,50); >>y=sin(x); >>z=cos(x); >>plot(x,y,x,z) % Alternatively, can use hold on >>plot(x,y); >>hold on >>plot(x,z,'g') Dr.Wanchak Lenwari :Control System and Instrumentation Engineering, KMUTT 13

14 Multiple Figure subplot divides the current figure into rectangular panes that are numbered rowwise. Each pane contains an axes. Subsequent plots are output to the current pane. subplot(m,n,p) creates an axes in the pth pane of a figure divided into an m-by-n matrix of rectangular panes. The new axes becomes the current axes. Dr.Wanchak Lenwari :Control System and Instrumentation Engineering, KMUTT 14

15 Multiple Figure Example: >>income = [ ]; >>outgo = [ ]; To plot income in the top half of a figure and outgo in the bottom half, >>subplot(2,1,1); plot(income) >>subplot(2,1,2); plot(outgo) Q1. If we want to plot income on the left and outgo on the right, which commands will you use? Dr.Wanchak Lenwari :Control System and Instrumentation Engineering, KMUTT 15

16 Multiple Figure Dr.Wanchak Lenwari :Control System and Instrumentation Engineering, KMUTT 16

17 Multiple Figure Dr.Wanchak Lenwari :Control System and Instrumentation Engineering, KMUTT 17

18 Exercise 2 If x is one cycle period (0-2pi), use matlab to make the plot shown. [15 mins] sin(x) cos(x) cos(x)and sin(x) cos(x+pi) and sin(x+pi) Dr.Wanchak Lenwari :Control System and Instrumentation Engineering, KMUTT 18

19 Plot Resolution 0.5x Plot y = 3.5 cos(5x) for 2 x 5 >>x=-2:0.001:5; % create x with spacing of >>y=(3.5).^(-0.5*x).*cos(5*x);% must use.^ and.* % (array calculation) >>plot(x,y) 3 If x spacing is 0.2, What is the 2 difference from the last plot? >>figure >> x=-2:0.2:5; % start new figure >>y=(3.5).^(-0.5*x).*cos(5*x);% >>plot(x,y) Dr.Wanchak Lenwari :Control System and Instrumentation Engineering, KMUTT 19

20 fplot command The fplot command can be used to plot a function y = f(x). The format is fplot( function,limits) The limits are vectors with the domain of x, and optionally with limits of the y axis: [xmin,xmax] or [xmin,xmax,ymin,ymax] x spacing will be calculated automatically. Line specifiers can be added. i.e. >>fplot('cos(x)',[-2*pi 2*pi]) Dr.Wanchak Lenwari :Control System and Instrumentation Engineering, KMUTT 20

21 Exercise 3 Plot y = x cos(5x) for 2 x 5 using fplot command [5 mins] Dr.Wanchak Lenwari :Control System and Instrumentation Engineering, KMUTT 21

22 End Dr.Wanchak Lenwari :Control System and Instrumentation Engineering, KMUTT 22