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MATLAB Basics: Matrix Manipulations, Programming, Graphics, Image Types, and Processing

An introduction to MATLAB, covering matrix manipulations, MATLAB programming, graphics, image types, and image processing. Includes useful functions and examples.

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MATLAB Basics: Matrix Manipulations, Programming, Graphics, Image Types, and Processing

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  1. Introduction MATLAB stands for MATrix LABoratory. Basics Matrix Manipulations MATLAB Programming Graphics Image types Image Processing Useful functions

  2. Basics • Basic data element is an array that does not require dimensioning. • A=[1 2 3;4 5 6; 7 8 9] A = [ 1 2 3 4 5 6 7 8 9]

  3. Matrix Manipulations • Sum(A) = sums of the columns of A • A’ = Transpose of A • Diag(A) = gives diagonal elements of A • Min(A) = minimum element column wise of A. • Max(A) = maximum element column wise of A. • Mean(A) = Average element column wise of A. • Std(A) = Standard deviation column wise of A. • X = zeros(5,5) Y = ones(6,6) • M=rand(5,5) N = randn(6,6) • A=[1:50] • A=[0:pi/4:pi]=[0 0.7854 1.5708 2.3562 3.1416]

  4. Matrix Manipulations (contd..) • B = magic(4) = [ 16 2 3 13 Dürer's magic square 5 11 10 8 9 7 6 12 4 14 15 1] • All numbers are stored internally using the long format specified by the IEEE floating-point standard. • Floating-point numbers have • finite precision16 significant decimal digits and • finite range 10-308 to 10+308.

  5. Matrix Manipulations (contd..) • A(:,2) = []  deletes 2nd column. • A(2:2:12) = [] results in row vector of remaining elements. • A = A.*5  Element-by-element multiplication. • [indices] = find(isprime(A)) • format  this command can be used for formatting the displayed numeric output (either in short or long format).

  6. MATLAB Programming MATLAB has several flow control constructs: • if statements • switch statements • for loops • while loops • continue statements • break statements

  7. Graphics • Plotting sinusoidal function using the plot function. • Cylinder  unit cylinder with default 20 points on the circumference. • Sphere  unit sphere with default 20 points on the circumference. • Subplot(m,n,p)  partitions the figure window into m-by-n matrix of small subplots and selects the pth subplot for the current plot.

  8. Graphics (contd..) • mesh produces wire frame surfaces that color only the lines connecting the defining points. • surf displays both the connecting lines and the faces of the surface in color. • Light and camera effect on the visualization of 2-dim sinc function (i.e. sin(r)/r) between x and y directions.

  9. Types of Images • Index images • Intensity images • Binary images • RGB images

  10. Image Processing • Dürer's magic square • Animation using EraseMode property. • Animation using Movie method • Functions: • Imread  read an image • Imwrite  writes specified matrix into an image. • Image  displays specified matrix as an image. • Imshow  Displays an intensity (gray level) image. • Im2frame  converts an image into movie frame. • Avifile  creates an avifile object. • Addframe  adds movie frame to avifile object. • Getframe  returns movie frame. • Movie  Play recorded movie frames. • close  closes current figure.

  11. Useful functions • help fnName  help on any function. • whos  information on current variables in the workspace. • guide  GUI editor. • demo  Matlab toolboxes and functions demo. • eval(str)  evaluates expression in the str variable. • load abc.mat  loads data in the matlab file.

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