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MATLAB for Scientists and Engineers

MATLAB for Scientists and Engineers. Numerical Computing with . Byoung -Jo CHOI, PhD University of Incheon. References. MATLAB Getting Started Guide, MathWorks MATLAB User's Guide, MathWorks

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MATLAB for Scientists and Engineers

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  1. MATLABfor Scientists and Engineers Numerical Computing with . Byoung-Jo CHOI, PhD University of Incheon

  2. References • MATLAB Getting Started Guide, MathWorks • MATLAB User's Guide, MathWorks • Mastering MATLAB 7, Duane Hanselman and Bruce Littlefield, Pearson/Prentice Hall, 2005 • Numerical Computing with MATLAB, Cleve Moler, MathWorks • 임종수의 MATLAB7, 높이깊이, 2009 • MATLAB: An Introduction with Applications, Amos Gilat, John Wiley & Sons, Inc., 2004 • Graphics and GUIs with MATLAB, 3rd Ed, Patrick Marchand and O. Thomas Holland, Chapman & Hall/CRC, 2003

  3. Script M-Files Numerical Computing with . MATLAB for Scientists and Engineers

  4. You will be able to • Write simple scriptm-files using the editor, • Get user inputs and print the formatted results, • Give explanations on your scripts using comments, • Use cell mode for efficient coding and evaluation, • Create a simple dialoguewindow, • Save and Load data to/from MATLAB data file, text file as well as Excel files • Use timer to perform repeated action

  5. What is Script M-File • Text file comprised of a series of MATLAB commands • The file name ends with .m, hence m-file. • MATLAB interprets the lines in a script m-file. • Example calc_price.m 1: 2: 3: 4: 5: % Calculate the total price nItem = input('Enter the number of items:'); uPrice = input('Enter the unit price:'); tPrice = nItem * uPrice; fprintf('The total price is %d.\n', tPrice);

  6. Launching M-File Editor 1/3 • 'New M-File' Toolbar Using Toolbar

  7. Launching M-File Editor 2/3 • 'File – New – M-File' Menubar Using Menubar

  8. Launching M-File Editor 3/3 • From Command History Window • Create m-file using the past commands Popup Menu

  9. Save and Run the Script • F5 to save the changes and run the entire script. Modified but Not Saved Yet! * Save Run All F5

  10. Evaluate the Selected Script • F9 to run the selected script. • Menubar: Text – Evaluate Section Using Hot Key F9 to Run the Selection

  11. Useful Functions for Scripts • For User Interactions beep pause pause(5) waitforbuttonpress sec echo on Echo MATLAB commands in scripts. echo off Act silently. Default mode. price = input('Enter the Unit Price: '); fprintf('The price is %d.\n', price * 20 ); number input name = input('Enter your name: ','s'); disp(name); string input keyboard Gives control to keyboard. Go into k>> mode Type R-E-T-U-R-N (5 characters) to exit. Debug Mode

  12. Getting User Inputs 1/2 • Getting user input from command line greetings_input.m % Get user inputs using command line name = input('Your name: ','s'); age = input('Your age: '); fprintf( ['Hello, %s!' ... ' You will be %d years old next year\n'], ... name, age+1); %% fprintf( 'Press key to continue..'); pause today1 = date; fprintf( '\nToday is %s.\n', today1 );

  13. Getting User Inputs 2/2 • Getting user input from dialog box greetings_dlg.m %% Get user inputs using dialog prompt = {'Your name', 'Your age:'}; dlg_title = 'Greetings'; num_lines = 1; def = {'Sam','21'}; answer = inputdlg (prompt,dlg_title,num_lines,def); name = answer{1}; age = str2num (answer{2}); msg = sprintf( 'Hello, %s! You will be %d years old next year\n', name, age+1); h = msgbox (msg, 'Greetings'); uiwait (h) today1 = date; msg = sprintf( '\nToday is %s.\n', today1 ); h = msgbox (msg, 'Greetings');

  14. Other Dialog Boxes errordlg helpdlg questdlg listdlg warndlg various_dlgs.m

  15. Comments • Line comments • Block comments % This m-file demonstrates filtering operation % of FIR designed for removing a tone noise. % Refer to Book1 for the exact algorithm % Three 2-R plot will be drawn. %{ This m-file demonstrates filtering operation of FIR designed for removing a tone noise. Refer to Book1 for the exact algorithm }% Useful for commenting out a block of code temporarily for debugging.

  16. Commenting Out • Ctrl+R for commenting out the selection • Ctrl+T for un-commenting out the selection

  17. Code Cells • Code blocks separated by %% %% Initializing Data Structure Fs = 1440; % Sampling frequency Ts = 1 / Fs; % Sampling Time F0 = 2.4e3; % Carrier frequency %% Generate Time Domain Signal t = 0:Ts:2; s = sin(2*pi*F0*t); %% Plot the Signal plot(t,s); Code Cell 1 Code Cell 2 Code Cell 3

  18. Enabling Cell Mode • When enabled, cell control toolbar appears.

  19. Evaluating the Cells • Run / Run & Go Ctrl Shift Enter + + Evaluate the cell and advance to the next cell. Ctrl Enter Evaluate the current cell. +

  20. Modify Parameter and Run the Cell • Increment / decrement a parameter by • Multiply / divide a parameter by plot_cosine.m Change the value near the cursor and execute the cell.

  21. Output Commands - disp • disp disp(name of a variable) ordisp('text as string') disp_demo.m n = [8 1 6] disp(n) % show the values of n disp('Magic Numbers') % just text disp(['The numbers are: ' num2str(n)]) % text and No's >> disp_demo n = 8 1 6 8 1 6 Magic Numbers The numbers are: 8 1 6

  22. Output Commands – fprintf 1/4 • fprintf fprintf('text') orfprintf('format',arg1, arg2,..) fprintf_demo.m n = [8 1 6]; fprintf( '%2d %2d %2d\n', n ); fprintf('Magic Numbers\nDo Exist!\n') % just text fprintf('The numbers are %d, %d and %d.\n', n) >> fprintf_demo 8 1 6 Magic Numbers Do Exist! The numbers are 8, 1 and 6. \n new line \t horizontal tab %d decimal integer %x hexadecimal %f floating point %*d field width, ..

  23. Output Commands – fprintf 2/4 • fprintf understands vectors and matrices • 2x multiplication table >> times2_table 2 x 1 = 2 2 x 2 = 4 2 x 3 = 6 2 x 4 = 8 2 x 5 = 10 2 x 6 = 12 2 x 7 = 14 2 x 8 = 16 2 x 9 = 18 times2_table.m n = (1:9)'; times2 = [ 2*ones(9,1) n 2*n ]; fprintf('%d x %d = %2d\n', times2') >> times2' ans = 2 2 2 2 2 2 2 2 2 1 2 3 4 5 6 7 8 9 2 4 6 8 10 12 14 16 18

  24. Output Commands – fprintf 3/4 • advanced formatting • field width and precision format_demo.m fprintf('%4d %d %5.1f %-5.1f %+5.1f\n', ... 2, 2, pi, pi, pi ); fprintf('%4d %d %5.1f %-5.1f %+5.1f\n', ... -2, -2, -pi, -pi, -pi ); >> format_demo 2 2 3.1 3.1 +3.1 -2 -2 -3.1 -3.1 -3.1 2 2 3 . 1 3 . 1 + 3 . 1 - 2 - 2 - 3 . 1 - 3 . 1 - 3 . 1

  25. Output Commands – fprintf 4/4 • Writing into a text file • Steps: fopen() fprintf() fclose() times2_table_file.m n = (1:9)'; times2 = [ 2*ones(9,1) n 2*n ]; fid = fopen('times2.txt','w'); fprintf(fid, '%d x %d = %2d\n', times2'); fclose(fid); times2.txt

  26. MATLAB Data File • save and load into/from MATLAB data file • save • load savemydata savemydata var1 var2 ... savemydata var3 -append save –ascii mydata.txt var1 loadmydata load mydata.txt

  27. Reading from Excel File 1/2 • xlsread • Interactive range selection a = xlsread('simple.xlsx',-1)

  28. Reading from Excel File 2/2 • xlsread • Read the entire excel file • Read a range of data from the excel file a = xlsread('simple.xlsx') a = xlsread('simple.xlsx','Sheet1','A3:B4')

  29. Writing to Excel File • xlswrite • Write data into an Excel file. xlswrite_demo.m % Excel write demo % Write to the first sheet beginning from A1 xlswrite('magic.xlsx', magic(4)); % Write to a new sheet, 'Magic5', beginning from A1 xlswrite('magic.xlsx', magic(5), 'Magic5'); % Write to 'Sheet2' beginning from A1 xlswrite('magic.xlsx', magic(6), 2); % Write to 'Sheet3' beginning from B2 xlswrite('magic.xlsx', magic(7), 3, 'B2');

  30. Timer • Repeated action using timer function repeated_hello.m t = timer('TimerFcn','say_hello','StartDelay',2, 'ExecutionMode','fixedDelay','Period', 3); start(t) fixedRate singleShot fixedSpacing stop(t) delete(t) StartDelay Period Period Period say_hello.m function say_hello load voices soundsc(hello,Fs) Try timer_demo.m!!

  31. Timer Demo • A man says 'Hello!' repeatedly. timer_demo.m % Timer demonstration ans = inputdlg('Period in seconds', ... 'Greeting Man Timer',1,{'3'}); period = str2double(ans{1}); t = timer('TimerFcn','say_hello','StartDelay',1, ... 'ExecutionMode','fixedDelay','Period', period); start(t); %% Listen to the voice for a while. h = msgbox('Do you want to stop the timer?' , ... 'Stop Timer'); uiwait(h); stop(t) delete(t)

  32. Start-up and Finish Script • User defined: startup.m, finish.m MATLAB matlabrc.m finish.m q='Sure?'; b=questdlg(q,'Exit Request','Yes','No','No'); switch b case 'No; quit cancel; end startup.m format compact cd c:\work pathdef.m edit startupsav.m

  33. Exercise 1 – Prime Factoring v1.0 • Write a script file, 'ifactor.m', which gets a number from user and prints the number as a product of the prime factors. (Hint: factor) >> ifactor Prime Factoring v1.0 Enter a positive integer:30 30 = 1 x 2 x 3 x 5 >> ifactor Prime Factoring v1.0 Enter a positive integer:40 40 = 1 x 2 x 2 x 2 x 5

  34. Solution 1 • Script • Screenshot of running 'ifactor' ifactor.m

  35. Exercise 2 – Prime Factoring v1.1 • Write a script file, 'ifactor2.m', which gets a number from user using a dialog box and prints the number as a product of the prime factors at a message box. [Hint: inputdlg(), msgbox()]

  36. Solution 2 • Script and Screenshot ifactor2.m

  37. Exercise 3 – Mean and Variance • Write a script file, 'icalc.m', which prints the mean and the variance of the data in 'marks.xlsx'. [Hint: mean(), var()]

  38. Solution 3 • Script • Screenshot of running icalc icalc.m

  39. Notes

  40. Notes

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