Introduction to MATLAB
اسلاید 1: Introduction to MATLABIran University of Science and Technology, Computer Engineering Department,Ehsan Adeli M. (eadeli@iust.ac.ir)
اسلاید 2: Outline2IntroductionMATLAB EnvironmentGetting HelpVectors, Matrices, and Linear AlgebraPlottingUser Defined FunctionsImage Manipulation and ProcessingAudio ProcessingFilters and OperationsMultimedia Systems (eadeli@iust.ac.ir)
اسلاید 3: IntroductionMATLAB Stands for MATrix LABoratory.The MATLAB environment allows the user to:manage variablesimport and export dataperform calculationsgenerate plotsdevelop and manage files for use with MATLAB.A script can be made with a list of MATLAB commands like other programming language.Multimedia Systems (eadeli@iust.ac.ir)3
اسلاید 4: EnvironmentMultimedia Systems (eadeli@iust.ac.ir)4
اسلاید 5: Getting HelpType one of following commands in the command window:help – lists all the help topichelp topic – provides help for the specified topichelp command – provides help for the specified commandhelp help – provides information on use of the help commandhelpwin – opens a separate help window for navigationlookfor keyword – Search all M-files for keywordOr simply press ‘F1’ and use the graphical help window.Multimedia Systems (eadeli@iust.ac.ir)5
اسلاید 6: VariablesVariable names:Must start with a letterMay contain only letters, digits, and the underscore “_”Matlab is case sensitive, i.e. one & OnE are different variables.Matlab only recognizes the first 31 characters in a variable name.when a semi-colon>> tutorial = 1234;>> tutorial = 1234”;” is placed at the end of each command, the result is not displayed.Multimedia Systems (eadeli@iust.ac.ir)6
اسلاید 7: Variables (Cont’d)Special variables:ans : default variable name for the result pi: π = 3.1415926…………eps: ∈ = 2.2204e-016, smallest amount by which 2 numbers can differ.Inf or inf : ∞, infinityNaN or nan: not-a-numberCommands involving variables:who: lists the names of defined variableswhos: lists the names and sizes of defined variablesclear: clears all variables, reset the default values of special variables.clear name: clears the variable nameclc: clears the command windowclf: clears the current figure and the graph window.Multimedia Systems7
اسلاید 8: Vectors>> x = [ 0 0.25*pi 0.5*pi 0.75*pi pi ]x =0 0.7854 1.5708 2.3562 3.1416>> y = [ 0; 0 25*pi; 0 5*pi; 0 75*pi; ]y =00.78541.5708 y2.35623.1416Multimedia Systems (eadeli@iust.ac.ir)8
اسلاید 9: Vectors (Cont’d)Vector Addressing – A vector element is addressed in MATLAB with an integer index enclosed in parentheses.>> x(3)The colon notation may be used to address a block of elements (start : increment : end)start is the starting index, increment is the amount to add to each successive index, and end is the ending index. A shortened format (start : end) may be used if increment is 1.>> x(1:3)ans =0 0.7854 1.5708NOTE: MATLAB index starts at 1.Multimedia Systems (eadeli@iust.ac.ir)9
اسلاید 10: Vectors (Cont’d)Multimedia Systems (eadeli@iust.ac.ir)10
اسلاید 11: Array OperationsScalar-Array Mathematics:Element-by-Element Array-Array Mathematics:Multimedia Systems (eadeli@iust.ac.ir)11
اسلاید 12: MatricesA Matrix array is two-dimensional, having both multiple rows and multiple columns, similar to vector arrays:It begins with [, and end with ]spaces or commas are used to separate elements in a rowsemicolon or enter is used to separate rows.Matrix Addressing:matrixname(row, column)colon may be used in place of a row or column reference to select the entire row or column.Multimedia Systems (eadeli@iust.ac.ir)12
اسلاید 13: Matrices (Cont’d)Multimedia Systems (eadeli@iust.ac.ir)13
اسلاید 14: Matrices (Cont’d)Multimedia Systems (eadeli@iust.ac.ir)14
اسلاید 15: Example, Linear EquationsMultimedia Systems (eadeli@iust.ac.ir)15
اسلاید 16: PlottingPlotting Curves:plot (x,y) – generates a linear plot of the values of x (horizontal axis) and y (vertical axis).semilogx (x,y) – generate a plot of the values of x and y using a logarithmic scale for x and a linear scale for ysemilogy (x,y) – generate a plot of the values of x and y using a linear scale for x and a logarithmic scale for y.loglog(x,y) – generate a plot of the values of x and y using logarithmic scales for both x and yMultiple Curves:plot (x, y, w, z) – multiple curves can be plotted on the same graph by using multiple arguments in a plot command. The variables x, y, w, and z are vectors. Two curves will be plotted: y vs. x, and z vs. w.legend (‘string1’, ‘string2’,…) – used to distinguish between plots on the same graphMultiple Figures:figure (n) – used in creation of multiple plot windows. place this command before the plot() command, and the corresponding figure will be labeled as “Figure n”close – closes the figure n window.close all – closes all the figure windows.Subplots:subplot (m, n, p) – m by n grid of windows, with p specifying the current plot as the pth windowMultimedia Systems (eadeli@iust.ac.ir)16
اسلاید 17: Plotting (Cont’d)Multimedia Systems (eadeli@iust.ac.ir)17
اسلاید 18: Flow ControlMultimedia Systems (eadeli@iust.ac.ir)18
اسلاید 19: Loopsbreak – is used to terminate the execution of the loop.Multimedia Systems (eadeli@iust.ac.ir)19
اسلاید 20: M-FilesA M-file is a group of MATLAB commands.MATLAB can open and execute the commands exactly as if they were entered at the MATLAB command window.To run the M-files, just type the file name in the command window. (make sure the current working directory is set correctly)Multimedia Systems (eadeli@iust.ac.ir)20
اسلاید 21: User Defined FunctionsAdd the following command in the beginning of your m-file:function [output variables] = function_name (input variables);Note that the file name should be the same as the function name.Multimedia Systems (eadeli@iust.ac.ir)21
اسلاید 22: Images in MATLABMATLAB can import/export several image formatsBMP (Microsoft Windows Bitmap)GIF (Graphics Interchange Files)HDF (Hierarchical Data Format)JPEG (Joint Photographic Experts Group)PCX (Paintbrush)PNG (Portable Network Graphics)TIFF (Tagged Image File Format)XWD (X Window Dump)MATLAB can also load raw-data or other types of image dataData types in MATLABDouble (64-bit double-precision floating point)Single (32-bit single-precision floating point)Int32 (32-bit signed integer)Int16 (16-bit signed integer)Int8 (8-bit signed integer)Uint32 (32-bit unsigned integer)Uint16 (16-bit unsigned integer)Uint8 (8-bit unsigned integer)
اسلاید 23: Images in MATLAB• Binary images : {0,1}• Intensity images : [0,1] or uint8, double etc. • RGB images : m-by-n-by-3• Indexed images : m-by-3 color map• Multidimensional images m-by-n-by-p (p is the number of layers)
اسلاید 24: Image import and exportRead and write images in Matlab>> I=imread(cells.jpg);>> imshow(I)>> size(I)ans = 479 600 3 (RGB image)>> Igrey=rgb2gray(I);>> imshow(Igrey)>> imwrite(lgrey, cell_gray.tif, tiff)Alternatives to imshow>>imagesc(I)>>imtool(I)>>image(I)
اسلاید 25: Images and MatricesHow to build a matrix (or image)?>> A = [ 1 2 3; 4 5 6; 7 8 9 ]; A = 1 2 3 4 5 67 8 9>> B = zeros(3,3) B = 0 0 00 0 00 0 0>> C = ones(3,3) C =1 1 11 1 11 1 1 >>imshow(A) (imshow(A,[]) to get automatic pixel range)
اسلاید 26: Image format conversionConvert between intensity/indexed/RGB to binary format:dither()Convert between intensity format to indexed format:gray2ind()Convert between indexed format to intensity format:ind2gray()Convert between indexed format to RGB format:ind2rgb()Convert a regular matrix to intensity format by scaling: mat2gray()Convert between RGB format to intensity format: rgb2gray()Convert between RGB format to indexed format:rgb2ind()Multimedia Systems (eadeli@iust.ac.ir)26
اسلاید 27: ColormapsI = imread (‘lena.bmp’);imshow (I);colormap (cool);Autumn, bone, colorcube, cool, copper, flag, gray, hot, hsv, jet, pink, prism, spring, summer, white, winterMultimedia Systems (eadeli@iust.ac.ir)27
اسلاید 28: Videomov = aviread(filename)mov = aviread(filename, index)fileinfo = aviinfo(filename)Multimedia Systems (eadeli@iust.ac.ir)28
اسلاید 29: Digital AudioMultimedia Systems (eadeli@iust.ac.ir)29
اسلاید 30: Audio[road,fs]=wavread(road.wav); The array road now contains the stereo sound data and fs is the sampling frequency. This data is sampled at the same rate as that on a music CD (fs=44,100 samples/second).The left and right channel signals are the two columns of the road array: left=road(:,1);right=road(:,2);Multimedia Systems (eadeli@iust.ac.ir)30
اسلاید 31: time=(1/44100)*length(left);t=linspace(0,time,length(left));plot(t,left)xlabel(time (sec));ylabel(relative signal strength)soundsc(left,fs) % plays left channel as mono soundsc(right,fs) % plays right channel mono (sound nearly the same) soundsc(road,fs) % plays stereo (ahhh…)Multimedia Systems (eadeli@iust.ac.ir)31
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