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Introduction to MATLAB

Introduction to MATLAB. Notes to complement on-line demo. MATLAB Overview. What is MATLAB A program that may be used to automate mathematical computations Interpretive environment, calculations at the command line Includes scripting language, you can write programs

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Introduction to MATLAB

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  1. BAE 1012 Introduction to MATLAB Notes to complement on-line demo

  2. MATLAB Overview BAE 1012 • What is MATLAB • A program that may be used to automate mathematical computations • Interpretive environment, calculations at the command line • Includes scripting language, you can write programs • Rich with engineering oriented functions • Modern engineering tool widely used in engineering • Includes “Toolboxes” for specialty applications • Controls • Signal Processing • Bio-system simulation • Includes block diagram based simulation “Simulink”

  3. Simple Calculations BAE 1012 • Command Line Interpreter • Set variables • A=3 • B=[3,4,7] row vector • C=[3; 4; 7] column vector • D=[1,2;3,4] matrix • Show variables • Who,whos • Clear variables • Clear, clear x • Set iterated list • E=1:0.2:10 (start : increment : end)

  4. Getting help BAE 1012 • Best: • Select Help from the menu (MATLAB 6) • Next Best (UNIX/LINUX): • Use the command HELP from the command prompt • “HELP” Alone for general – list topic areas • “Help topic” for help on “topic” • Topics are divided into general areas • Controls, Signal processing, etc. • Local functions may be added to the local dir • Organized with • General help • Toolbox help

  5. Complex Numbers BAE 1012 • Set number • A=3 + 4i • Magnitude • M=abs(A) • Angle • Alpha=angle(A) • Conjugate • A_star=conj(A) • Imaginary part / real part • Imag_a = imag(A) • Real_a=real(A) • Try sqrt(-1)

  6. Simple Plotting BAE 1012 • Simple x/y plot • x=0:1:20 • x=sin(x) • plot(x,y) • Set line /point type • plot(x,y,’c+’) cyan “+” points • plot(x,y,’c+’,x,y,’y-’) cyan points and yellow line • Set Titles and labels Labels • xlabel(‘X-axis’), Ylabel(‘Y-Axis’) • Title(‘Title’) • Alternative: Use figure menu /Edit/Axis Properties • Set axis titles • Main title • Line properties etc.

  7. 3D plot BAE 1012 • Set x and y values • x = 0:.1:20; • y = 0:.1:20; • Create matrices for “xg – yg” grid • [xg, yg] = meshgrid(x,y); • Calculate an equation for “z” on the grid • z = sin(pi*xg/20).* sin(pi*yg/20); (note the .* for element by element multiplication where xg and yg are 20x20 matricies) • Plot the surface or mesh • surf(x,y,z) or mesh(x,y,z)

  8. Matrix math BAE 1012 • Consider a set of equations: • Given x1,x2 you can find y1,y2. • The more usual problem is y1,y2 are given and you need x1,x2 • Solution: • Write in matrix form and solve

  9. Matrix math BAE 1012 • Example • Set y,A • Y = [ 3 ; 4 ] • A = [ 7 , 4.5; 3.3, 9.1 ] • Find A inverse (A-1) • Ai = inv(A) • Calculate x • x = Ai*y

  10. Additional matrix operations BAE 1012 • Transpose a matrix • (switch rows and columns) • y = y’ • To multiply element by element by a scalar • y = sin(y) .* y (replace each element by “y sin y”)

  11. M-File -programs BAE 1012 • Use File menu to create or open a script file • Use Matlab commands as script • Save into m-file space and then execute by file name on the command line • Example: • Save as sin_surf.m • Execute as sin_surf on the command line for i = 1:30 for j = 1:30 z(i,j) = sin(3.14159 * ((i - 16) ^ 2 + (j - 16) ^ 2) / (7 * 30)) *( j - 1); end end surfc(z)

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