Engineering Innovation Center MATLAB Basics

Transcription

1 Engineering Innovation Center MATLAB Basics

2 MATLAB Short for MATrix LABoratory Both a programming language and the interface Designed to deal with large sets of data and analysis Allows matrix manipulations, plotting of functions and data, implementation of algorithms, creation of user interfaces, and interfacing with programs written in other languages, including C, C++, Java, Fortran and Python Available free through A&M Software Portal: software.tamu.edu

3 MATLAB - Interface Interface is broken into multiple parts Most of what is done involves the Editor, Command Window, and Workspace The Editor is where you write MATLAB scripts The Workspace is where all variable currently defined are shown The Command Window provides a live interface to MATLAB, where code typed in is immediately evaluated

4 MATLAB Workspace The Workspace is primarily used to track values of variables in the program In addition, it can be used to edit and add variables to the current working environment Also provides useful data about arrays such as minimum, max, mean, and other selectable information

5 MATLAB Variables and Types In MATLAB, data is stored in variables Variables consist of many types, but primarily consist of numerical types (integers, doubles, floats), character strings, and arrays Variables provide a means to manipulate data and store it during the program execution Variable s values can be viewed in the Workspace Variable names can only begin with letters or underscore, and cannot contain spaces an_int = 3; a_double = 4.423; a_string = 'abcdefg123'; an_array = [1, 2, 3, 4, 5, 6];

6 MATLAB Arrays and Matrices Arrays are the means that MATLAB provides to store matrix like data Arrays can be treated like matrices or as sets of data depending on necessity Adding a. to operators makes them compatible with matrices Arrays are addressable meaning they can be operated on per element using parentheses to select values Use the pneumonic RC Cola to remember row column is the addressing order an_array = [ ; ; ]; % 3x3 array another_array = [ 1 ; 1 ; 1 ]; % 3 x 1 array a = an_array(1,2) % returns the value 2, row 1 column 2 a = an_array.* 3; % returns the array multiplied by 3

7 MATLAB-Loops With loop control statements, you can repeatedly execute a block of code There are two types of loops: for statements loop a specific number of times, and keep track of each iteration with an incrementing index variable while statements loop as long as a condition remains true Each loop requires the end keyword It is a good idea to indent the loops for readability x = (1,10); for n = 2:6 end n = 1; x(n) = 2 * x(n - 1); preallocate a 10-element vector, and calculate five values nfactorial = 1; while nfactorial < 1e100 end n = n + 1; nfactorial = nfactorial * n; find the first integer n for which factorial(n) is a 100-digit number

8 MATLAB Calling functions MATLAB provides an extensive library of predefined functions These functions are called in the format of FunctionName(parameters); For example, one common function is dot() dot() is called with two parameters that are arrays, so it is used as c = dot(a, b); with a and b being arrays fprintf() is another commonly used function for outputting formatted text

9 MATLAB Plotting and Graphs MATLAB has a very detailed plotting library, allowing for various different kinds of graphs and styles to be generated For basic plots, plot(), scatter(), and ezplot() will serve most purposes plot can be used with two parameters, X and Y, which are arrays of equal size where each contained a correlating x and y value scatter can be used the same way ezplot can be used with functions directly, such as ezplot( x^2 ) which will plot the function y=x 2 For more specifics and formatting go to ics.html (MathWorks graphics documentation)

10 MATLAB Resources Google first thing to try, some has likely already asked your question MathWorks documentation Every part of MATLAB fully documented with examples stackoverflow.com Best resource for MATLAB questions that may be more specific error based questions