Basic MATLAB Tutorial

Transcription

1 Basic MATLAB Tutorial This is a basic tutorial for the Matlab program which is a high-performance language for technical computing for platforms: - Linux, - MS Windows - Mac Feb 2018 MATLAB integrates computation, visualization, and programming in an easy-to-use environment where problems and solutions are expressed in familiar mathematical notation Typical uses include - Math and computation - Algorithm development - Data acquisition Modeling, - simulation, and prototyping - Data analysis, - Scientific and engineering graphics - Curve fitting - etc

2 Basic Commands * help command get help for a command * clear clears all the memory (workspace) * clear x removes variable x from the memory * whos lists all the variables (and details) on the workspace * Semicolon (;) at the will suppress the output * Command history: upper & lower arrows, also command name guess * If you don t use a variable name, your calculation is labeled and assigned by ans variable Variables >> x = 4; >> y = sqrt(x) + 2 y = 4 Arrays >> A = [ ]; >> B = [ ]; >> A*B ans = >> A/B ans = inf >> A^B ans = Complex Numbers >> z = 3 + 4i; >> abs(z) Matrices >> B = [1 2 3;0 5 6;7 8 9] B = >> det(b) ans = -24 >> v = 0:8 v = >> v = 0:2:8 v = >> g = [ ] >> g(4:) ans = >> a = [1 2 3]' a = Basic Statistics >> x = [ ]; >> sum(x) ans = >> mean(x) ans = >> std(x) ans = >> min(x) ans = 1 >> length(x) >> max(x) ans = >> [value index] = max(x) value = index = 4 >> inv(b) Ans = >> M = [1 2; 3 4]; >> N = [0 1; 8 5]; >> M*N ans = Special Matrices >> P = zeros(2,2) P = >> P = zeros(2,1) P = 0 0 >> Q = ones(2,2) Q = >> I = eye(2) % unit matrix I = >> rand(2,2) % random matrix ans =

3 Some Intrinsic Functions Function Description abs(x) x sin(x) sine of x (x is in radian) cos(x) cosine of x tan(x) tangent of x sind(x) sine of x (x is in degrees) cosd(x) cosine of x tand(x) tangent of x asin(x) angle in radian from sin(x) acos(x) angle in radian from cos(x) atan(x) angle in radian from tan(x) log(x) ln(x) log10(x) log 10 (x) exp(x) e x mod(x,y) x modulo y (mod(12,5) = 2) size(a) Number of rows and columns of matrix A Solutions of linear algebraic equations Solve the following linear equitation: x + y + z = 6-2x + y = 0 3x + 2y + z = 10 >> A = [1 1 1; ; 3 2 1]; >> b = [6 0 10]'; >> x = inv(a) * b x = Derivative (matlab symbolic calc) Find the first and second derivative of the function f(x) = x 2 + exp(-x) >> diff(x^2+exp(-x)) % 1st derivative ans = 2*x-exp(-x) >> diff(x^2+exp(-x),2) % 2nd der ans = 2+exp(-x) Find first derivative of f(x) = x 2 + exp(-x) at x=3 >> d = diff(2*x^2); >> x = 3; >> eval(d) ans = 12 Roots of Equations Find the roots of polynomial x 5 + 2x 4 5x 3 + x + 3 = 0 >> c = [ ]; >> roots(c) ans = i i i i Find the root of sin(x)+2-x=0 >> solve('sin(x)+2-x=0') ans = Integration Find the indefinite integral and definite for the range [1, 2] of the function f(x) = x 2 + exp(-x) >> int(x^2+exp(-x)) % indefinite integral ans =1/3*x^3 - exp(-x) >> int(x^2+exp(-x),1,2)% definite integral ans = 7/3-exp(-2)+exp(-1) ans = 25659

4 Plotting >> x = -2*pi:01:4*pi; >> y = sin(x)/x; >> plot(x, y) >> xlabel('distance (m)') >> ylabel('speed (m/s)') >> grid on Reading Data file Consider you have two column data file called datatxt Let its content be: In MATLAB command line you can read and plot data as follows: >> [x y] = textread('datatxt'); >> plot (x,y,'*') >> axis([ ]) M files (1)Save the following lines to a file called toplam A = input('a = '); B = input('b = '); C = A + B; disp(c) >> topla A = 2 B = 3 5 (2)Save the following lines to a file called cizm x = -2*pi:01:4*pi; y = sin(x)/x; plot(x, y) xlabel('distance (m)') ylabel('speed (m/s)') grid on >> ciz Functions (1) Greate an m-file: >> edit hipom Type the followings in the editor: function y = hipo(x,y) y = sqrt(x^2 + y^2); >> hipo(3,4) (2) Greate an m-file: >> edit cat2polm Type the followings in the editor: function [r, t] = car2pol(x, y) r = sqrt(x^2 + y^2); t = atand(y, x); >> [uzaklik, aci] = car2pol(3,4) uzaklik = 5 aci = 53130

5 If statement Comparison Operators < Less than <= Less than or equal to > Greater than >= Greater than or equa to == Equal to ~= Not equal to Logical Operators & AND OR ~ NOT Example: gradem % Grade calculator mt1 = input('input mt1 '); mt2 = input('input mt2 '); fin = input('input fin '); avr = 03*mt1 + 03*mt2 + 04*fin; grade = 'A'; if avr<40 grade = 'F' elseif avr>=40 & avr<50 grade = 'D' elseif avr>=50 & avr<60 grade = 'C' elseif avr>=60 & avr<70 grade = 'B' elseif avr>=80 & avr<90 grade = 'A' else grade = 'A+' Loops while 1 disp('') for x = -5:5 if x == 0 break fprintf('%f %f\n',x,1/x) >> edit turevm % derivative calculator f = inline ('2*x^2 + exp(-x)'); x = 30; for i = 1:6 h = 1 / 10^i; f1 = (f(x+h)-f(x-h)) / (2*h); f2 = (f(x+h)-2*f(x)+ f(x-h)) / (h^2); fprintf('%d %f %f %f\n',i,h,f1,f2) a = 0:02:5 plot(a,f(a),'r-*') Graphical User Interface (GUI) See lecture notes at: Curve Fitting Tool Type the followings to start >> cftool Formatting output >> format short ans = >> format long ans = >> format rat ans = 355/113 EOF