CSC 422 Tutorial MATLAB I, Spring 2012

Matlab Tutorials 10 / 04 / 2006 2 • Introduction to Matlab • Working with Matlab • Image Processing using Matlab • Class Project 3 Introduction • MatLab : Matrix Laboratory • Numerical Computations with matrices • Every number can be represented as matrix • Why Matlab? • User Friendly (GUI) • Easy to work with • Powerful tools for complex mathematics 4 Command Window Command History Workspace Fig: Snap shot of matlab 5 Matrices in Matlab • To enter a matrix 3 1 6 4 >> A = [3 1 ; 6 4] >> A = [3, 1 ; 6, 4] >> B = [3, 5 ; 0, 2] Examples during Matlab demo 6 Basic Mathematical Operations Addition: >> C = A + B Subtraction: >> D = A – B Multiplication: >> E = A * B (Matrix multiplication) >> E = A .* B (Element wise multiplication) Division: Left Division and Right Division >> F = A . / B (Element wise division) >> F = A / B (A * inverse of B) >> F = A . \ B (Element wise division) >> F = A \ B (inverse of A * B) Examples during Matlab demo 7 Matrix with ZEROS: >> Z = ZEROS (r, c) Matrix with ONES: >> O = ONES (r, c) IDENTITY Matrix: >> I = EYE (r, c) r  Rows c  Columns zeros, ones, eye  Matlab functions Generating basic matrices Examples during Matlab demo 8 • Need help ? • HELP <function name> • LOOKFOR <key word> • Case sensitive • M files (.m) • To write and save matlab commands • Save time and easy to debug • Use of semicolon (;) • Comments (%) • Documentation • www.mathworks.com Making the best from Matlab Examples during Matlab demo 9 Image processing and matlab • Easy to work with; as Images are matrices • Built in functions for complex operations and algorithms (Ex. FFT, DCT, etc…) • Image processing tool box (?) • Supports most image formats (.bmp, .jpg, .gif, .tiff etc…) Examples during Matlab demo 10 Image processing in matlab To read and display images • im = imread(“filename.fmt”) • im is r x c if gray scale • im is r x c x 3 if color image (RGB) • imshow(im) % displays image • imwrite(im, “filename.fmt”) % writes image Size of image • [r c] = size(im) Examples during Matlab demo 11 Working with complex numbers • real and imaginary • real % real part of complex number • imag % imaginary part of complex number • magnitude and phase • abs % magnitude of complex number • angle % phase of complex number Examples during Matlab demo 12 Plotting / displaying • PLOT(x,y) • Plots y versus x. • Linear plot • XLABEL(‘label’) • YLABEL(‘label’) • TITLE(‘title’) • IMAGE(x) • Displays image 3D plots: • MESH • 3D mesh surface (Ex. filters) • MESHGRID • Useful in 3D plots • SURF • 3D colored surface (Ex. filters) Examples during Matlab demo