1. Getting Started MATLAB fundamentals Dr. Umakant Dwivedi 15/10/2009

2. 2 What is Matlab MATLAB® is a high-performance language for technical computing. It integrates computation, visualization, and programming in an easy-to-use environment where problems and solutions are expressed in familiar mathematical notation.

3. 3 Typical uses for Matlab Math and computation Algorithm development Data acquisition Modeling, simulation, and prototyping Data analysis, exploration, and visualization Scientific and engineering graphics Application development, including graphical user interface building

4. 4 More about Matlab MatLab is an interactive system whose basic data element is an array that does not require dimensioning. The name MatLab stands for MATrix LABoratory MatLab features a family of add-on application- specific solutions called toolboxes Toolboxes are comprehensive collections of MatLab functions (M-files) that extend the MatLab environment to solve particular classes of problems

5. 5 How to start and exit Matlab On a Microsoft Windows platform, to start MATLAB, double-click the MATLAB shortcut icon on your Windows desktop. After starting MATLAB, the MATLAB desktop opens Note the >> is the matlab command prompt To end your MATLAB session, select Exit MATLAB from the File menu in the desktop, or type quit in the Command Window. Note that nothing is saved when you exit, you will not be prompted to save

6. 6 MATLAB Desktop When you start MATLAB, the MATLAB desktop appears, containing tools (graphical user interfaces) for managing files, variables, and applications associated with MATLAB. The first time MATLAB starts, the desktop appears as shown in the following illustration, although your Launch Pad may contain different entries.

7. 7 Double Click on Icon Will open MATLAB

8. 8

9. 9 MATLAB Desktop, Cont. When launching Matlab, version 6.5/7 brings up a desktop with pull-down menus and various windows. These windows are:  Command Window: This is the main window for issuing commands and seeing results,  Current Directory: The files in the user directory currently available for use in the Command Window.  Workspace: a list of variables that have been used in the Command Window.  Command History: An ordered list of all commands issued in the Command Window.

10. 10 Command Window Working Memory Command History

11. 11 Calculator functions work as you'd expect: >>(1+4)*3 ans = 15 + and - are addition, / is division, * is multiplication, ^ is an exponent. You can assign variables from the matlab workspace.  Everything in matlab is a matrix. (If it's a scalar, it's actually a 1x1 matrix, and if it's a vector, it's an Nx1 or 1xN matrix.)  >>a = 3 ;  >>b=5*a;  >>c=b;

12. 12 Interactive Calculations Matlab is interactive, no need to declare variables >> 2+3*4/2 >> a=5e-3; b=1; a+b Most elementary functions and constants are already defined >> cos(pi) >> abs(1+i) >> sin(pi)

13. 13 To create a vector is pretty similar.  Each element is separated by spaces, the whole vector is in square brackets:  >>v = [1 3 6 8 9] To create a vector of values going in even steps from one value to another value, you would use  >>b = 1:.5:10 To turn a row vector into a column vector, just put a ' at the end of it. (This is also how to get the transpose of a matrix.) To create a matrix, you could do something like:  c = [1 3 6; 2 7 9; 4 3 1]  The semicolons indicate the end of a row. All rows have to be the same length.

14. 14 Command Window Getting help from the command window help (show the help document for a given function)

15. 15 Arithmetic operation The basic arithmetic operations on matrices are:  + addition  - subtraction  * multiplication  / division  ^ power  ‘ conjugate transpose

16. 16 element-by-element operations MATLAB provides element-by-element operations by prepending a ‘.’ before the operator .* multiplication ./ division .^ power .’ transpose (unconjugated)

17. 17 Relational operations MATLAB defines the following relational operations:  < less than  <= less than or equal to  > greater than  >= greater than or equal to  == equal to  ~= not equal to

18. 18 Logical operations MATLAB defines the following logical operations:  & and  | or  ~ not

19. 19 Math functions The following functions operate element-wise when applied to a matrix: sincostan asinacosatan sinhcoshtanh explog(natural log)log10 abssqrtsign

20. 20 Generating matrices Matrix building functions: >> A=zeros(m,n)  returns an m-by-n matrix of zeros >> A=ones(m,n)  returns an m-by-n matrix of 1s >> A=eye(m,n)  returns an m-by-n matrix with 1's on the diagonal and 0's elsewhere

21. 21 Generating random matrices >> A=rand(m,n)  returns an m-by-n matrix of random numbers whose elements are uniformly distributed in the interval (0,1) >> A=randn(m,n)  returns an m-by-n matrix of random numbers whose elements are normally distributed with mean 0 and variance 1 >> A=randint(m,n,range)  generates an m-by-n integer matrix. The entries are uniformly distributed and independently chosen from the range: [0, range-1] if range is a positive integer [range+1, 0] if range is a negative integer

22. 22 Accessing matrix elements Elements of a matrix are accessed by specifying the row and column >> A=[1 2 3; 4 5 6; 7 8 9]; >> x=A(1,3)  Returns the element in the first row and third column >> y=A(2,:)  Returns the entire second row [4 5 6]  “:” means “take all the entries in the column” >> B=A(1:2,1:3)  Returns a submatrix of A consisting of rows 1 and 2 and all three columns [1 2 3; 4 5 6]

23. 23 Complex numbers Some useful operations on complex numbers:  Complex scalar >> x = 3+4j  Real part of x >> real(x) ->3  Imaginary part of x >> imag(x) ->4  Magnitude of x >> abs(x) ->5  Angle of x >> angle(x) ->0.9273  Complex conjugate of x >> conj(x) ->3 - 4i

24. 24 Complex numbers Examples  x=5+3i and y= -3+1.5i  Finding, Real part of x,Imaginary part of x, Magnitude of x, Angle of x, Complex conjugate of x  Find x+y, x-y, x.y, x/y  V=230 angle 30 deg. and I=10 angle -30 deg.  Calculate Complex power S=V.I*, Real and reactive powers

25. 25 Flow control If statements if expression statements else statements end  Example If n<0 a=a-1; else a=a+1; end

26. 26 Flow control For  Repeats a group of statements a fixed, predetermined number of times. a=0; for n = 1:10 a=a+1; end

27. 27 Flow control WHILE  WHILE Repeat statements an indefinite number of times. The general form of a WHILE statement is: WHILE expression statements END.  Example a=0; b=5; while (a<25) a=a+1; end

28. Loading XLS File into MatLab and Plotting

29. 29 Loading an Excel File: Open MatLab Select Import Data from the File menu in the MatLab, OR double click on the data file in the Current directory window. Double Click on your Data file

30. 30 Loading an Excel File: A new window named Import Wizard as shown below should pop-up (in few seconds). Select Create vector then Click Finish button

31. 31 Plotting variables from workspace: To plot y Vs x graph. Click on variable x then press Ctrl button and select variable y Step 1 Step 2 Click on plot button Plot(x,y) >> plot(Time,Rdata) OR use plot command

32. 32 Click on Insert button on the toolbar pallets as shown in the 2nd figure to add Title, X,Y-axis name and legend

33. 33 After adding Title etc. You can save the figure or copy it and

34. 34 Final Graph

35. 35 Plotting using plot command The basic syntax to get a plot in matlab is plot(x1,y1)  (The x values always come before the y values, x1 and y1 represent variables that your data is stored in.) If you type a second plot command later, it will clear your first plot. If you type "hold on" it will hold the current plot so you can add plots on top of one another (until you reset it by typing "hold off".)  You can plot multiple values with plot(x1,y1,x2,y2) and you can specify the color and linetype of a plot as something like plot(x1,y1,'w*') to get white *'s for each data point

36. 36 To split your plot into a bunch of smaller plots, you can use the subplot command to split it up into rows and columns. subplot(r,c,n)  will split the plot window into r rows and c columns of plots and set the current plot to plot number n of those rows and columns. You can add titles, labels, and legends to plots.  title('This is a Title')  xlabel('My X axis')  ylabel('My Y axis')  legend('First Thing Plotted','Second Thing Plotted')

37. 37 Printing, Saving, and Loading Basic printing >>print –Pprintername You can also save to a Postscript or Encapsulated Postscript file: >>print -dps filename.ps >>prind -deps filename.eps You can also save your plot as an m-file (matlab script) which should contain all the commands you need to recreate your plot later. >>print -dmfile filename.m

38. 38 You can save and load files as either text data or matlab's own data format. If you have a text file consisting of a bunch of columns of data separated by spaces or tabs, you can load it into matlab with load filename.dat The above command will give you a matrix called filename. Then you can reassign columns of that matrix, i.e. col1 = filename(:,1);

39. 39 When you save data using the command  save filename.mat matlab will save all of your variables and their values in its own format, so that when you load it using  load filename.mat you will have all of your variables already defined and names.

40. Advanced operations in Matlab

41. 41 Variables MATLAB does not require any type declarations!  Real scalar:>> x=1  Complex scalar:>> x=1+2i  Row vector:>> x=[1 2 3]  Column vector:>> x=[1; 2; 3]  2x2 Matrix:>> x=[1 2; 3 4] You can define global variables by putting in front the variable the statement global.

42. 42 Complex numbers Some useful operations on complex numbers:  Complex scalar >> x = 3+4j  Real part of x >> real(x) ->3  Imaginary part of x >> imag(x) ->4  Magnitude of x >> abs(x) ->5  Angle of x >> angle(x) ->0.9273  Complex conjugate of x >> conj(x) ->3 - 4i

43. 43 Generating vectors >> x=[a:step:b]  Generate a vector that takes on the values a to b in increments of step >> x=linspace(a,b,n)  generates a row vector x of n points linearly spaced between a and b >> x=logspace(a,b,20)  generates a logarithmically spaced vector x of n points between 10^a and 10^b.

44. 44 M-files MATLAB is an interpretive language M-files are text files containing MATLAB scripts Scripts are sequences of commands typed by an editor The instructions are executed by typing the file name in the command window at the MATLAB prompt All the variables used in the m-file are placed in MATLAB’s workspace that contains all the variables defined in the MATLAB session

45. 45 Flow control If statements if expression statements else statements end  Example If n<0 a=a-1; else a=a+1; end

46. 46 Flow control For  Repeats a group of statements a fixed, predetermined number of times. a=0; for n = 1:10 a=a+1; end

47. 47 Function in Matlab To simplify your matlab file structure, you can use functions. An example of how to use matlab functions is the following: Main Matlab Program a = 10; b = 20; c = my_sum(a,b); Function declaration: function y = my_sum(m,n) y = m + n ; return(y) // give the file name of function same as function name e.g. my_sum.m

48. 48 Matlab Statements and Variables MATLAB is an expression language. It interprets and evaluates expressions typed in the command window at the keyboard. You are allowed to assign a name to an expression. Statements are usually in the form of variable = expression, e.g. A = magic(4)

49. 49 Creating a plot >> plot(x,y)  produces a graph of y versus x, where x and y are two vectors x=linspace(0,2*pi,100); plot(x,sin(x));

50. 50 Axis lables and titles xlabel('string')  labels the x-axis of the current axes ylabel('string')  labels the y-axis of the current axes Title(‘string’)  add a title to a graph at the MATLAB command prompt or from an M-file

51. 51 The figure function MATLAB directs graphics output to a figure window Graphics functions automatically create new figure windows if none currently exist >>figure  creates a new window and makes it the current figure >>clf  Clear current figure window

52. Thank You!