COMP MATLAB.

Transcription

1 COMP MATLAB

2 M 2

3 M 3

4 M 4

5 M 5

6 M 6

7 M script MATLAB MATLAB 7

8 M function M function [y1,...,yn] = myfunc(x1,...,xm) myfunc x1,...,xm y1,...,yn eters 8

9 function y=myfunc(x) y=x+1; >> myfunc(3) ans = 4 1 >> myfunc(4) ans = 5 9

10 function addtwo(x,y) % ADDTWO(x,y) Adds two numbers, vectors, whatever, and % print the result = x + y % Yang Chen, Mar. 3, 2018 disp(x+y); o MATLAB function / o H1 % H1 o H1 % / o % M o 10

11 >> help addtwo addtwo: Adds two numbers or vectors, and print the result = x + y >> addtwo(1,2) 3 o MATLAB o H1 11

12 v.s. function (function declaration line) MATLAB function workspace 12

13 myfunc: function [y] = myfunc(x) z=x+1; y = z*z; z 1 z z z z Command Window: >> z=3 z = 3 >> myfunc(4) z = 5 ans = 25 >> z z = 3 13

14 14

15 x X MATLAB

16 >> x=1 x = 1 >> X=2 X = 2 >> whos Name Size Bytes Class Attributes X 1x1 8 double x 1x1 8 double 16

17 >> dir MATLAB dir. NCSim_RECDF_169.eps.. Ranking_Accuracy_169.eps >> dir=1 dir = 1 >> dir dir = 1 17

18 1 18

19 2 global X_Val 19

20 3 persistent M MATLAB MATLAB [] a persistent a 20

21 MATLAB pi Inf ( ) i, j eps(n) realmax realmin NaN Not-a-number ( ) 5 >> pi*(5^2) ans = >> realmin ans = e-308 >> realmax ans = e

22 >> iskeyword' ans = Columns 1 through 7 'break' 'case' 'catch' 'classdef' 'continue' 'else' 'elseif' Columns 8 through 14 '' 'for' 'function' 'global' 'if' 'otherwise' 'parfor' Columns 15 through 20 'persistent' 'return' 'spmd' 'switch' 'try' 'while' MATLAB 20 22

23 MATLAB if-else- switch-case try-catch for while 23

24 MATLAB <statement-1> <statement-2> <statement-n> 24

25 lecture3_exp1.m % r r=5; % S=pi*r*r; % S >> lecture3_exp1 S =

26 if-else- if-else- (1) expression if expression <statements> 26

27 if-else- (2) if expression <statements_1> else <statements_2>

28 if-else- (3) n (n>2) if expression1 <statements_1> elseif expression2 <statements_2> else <statements_n> expression1 1 expression1 experssion2 2 n 28

29 if-else- function y=myfunc(a) if (mod(a,2)) disp(a); >> myfunc(1) 1 >> myfunc(2) >> myfunc(4) >> myfunc(9) 9 a a 1 29

30 if-else- function myfunc(n) if (mod(n, 2)) disp('odd'); else disp('even'); >> myfunc(10) even >> myfunc(3) odd >> myfunc(8) even n 2 30

31 if-else- function y=myfunc(point) if (point > 90) y=4; elseif (point > 80) y=3; elseif (point > 70) y=2; else y=1; >> myfunc(91) ans = 4 >> myfunc(71) ans = 2 >> myfunc(60) ans =

32 switch-case Switch case otherwise switch switch value case test1 <statement_1> case test2 <statement_2> otherwise <statement_n> 32

33 switch-case switch-case switch value == i strcmp MATLAB 33

34 e c e c (( )) a B e c T A M c e c B a L L B B e c A e (( e c >> a={'matlab',20;ones(2,3),1:10} a = 2 2 cell array 'matlab' [ 20] [2 3 double] [1 10 double] >> a(1, 1) ans = cell 'matlab' >> a(1, 2) ans = cell [20] 34

35 switch-case n = input('enter a number: '); switch n case -1 disp('negative one') case 0 disp('zero') case 1 disp('positive one') otherwise disp('other value') Input MATLAB Enter MATLAB n 1 positive one n 3 other value 35

36 switch-case function myfunc(day) switch (day) case {1, 2, 3, 4, 5} disp('weekday'); case {6, 7} disp('week'); otherwise disp('invalid'); >> myfunc(2) weekday >> myfunc(7) week >> myfunc(0) invalid >> myfunc(1) weekday / 36

37 switch v.s. if if if switch switch 37

38 try-catch try <statements_1> catch <statements_2> (1) MATLAB 1 2 (2) try-catch 38

39 try-catch function myfunc(a, B) try [A B] catch disp('dimension Mismatch') A B >> myfunc([1 1; 2 2], [1 1]) Dimension Mismatch >> myfunc([1 1; 2 2], [1 1]') ans =

40 for for for x=array <statements> for x for for x array 40

41 for Start ç array for x=1:3 disp(x); array N Stop Y ç array 41

42 for s = 0; for i=1:10 s=s+i; disp(s); 55 42

43 for Outer Loop for <loop_variable1>=<array1>: <statements (optional)> for <loop_variable2>=<array2>: <statements> <statements (optional)> Inner Loop ü 43

44 for A = zeros(2,3); for j = 1:2 for k = 1:3 A(j,k) = j + k; A A =

45 for function [m] = myfunc(x) m = zeros(x, x); for i = 1:x for j=1:x m(i, j) = 1/(i+j-1);! # # # # H = # # # # # "# $ & & & & & & & & & %& >> myfunc(4) ans =

46 for for i=1:5 for j=1:i fprintf('*'); fprintf('\n'); * ** *** **** ***** 1) i=1; j=1; 2) i=2; j=1; 3) i=2; j=2; 4) i=3; j=1; 5) i=3; j=2; 6) i=3; j=3; 7) i=4; j=1; 8) i=4; j=2; 9) i=4; j=3; 10) i=4; j=4; 11) i=5; j=1; 12) i=5; j=2; 13) i=5; j=3; 14) i=5; j=4; 15) i=5; j=5; 46

47 while while while expression <statements> 47

48 while Start x=0; while(x<1) disp(x); x=x+1; expression Y N Stop 48

49 while: Outer Loop while <expression1> <statements(optional)> while <expression2> <statements> <statements(optional)> Inner Loop 49

50 while n = 10; f = n; while n > 1 n = n-1; f = f*n; disp(['n! = ' num2str(f)]) n! =

51 while i=1; while (i<6) j=0; while (j<i) fprintf('*'); j=j+1; fprintf('\n'); i=i+1; * ** *** **** ***** 1) i=1; j=0; 2) i=2; j=0; 3) i=2; j=1; 4) i=3; j=0; 5) i=3; j=1; 6) i=3; j=2; 7) i=4; j=0; 8) i=4; j=1; 9) i=4; j=2; 10) i=4; j=3; 11) i=5; j=0; 12) i=5; j=1; 13) i=5; j=2; 14) i=5; j=3; 15) i=4; j=4; 51

52 return input pause continue break 52

53 return MATLAB commands return MATLAB 53

54 return function y=myfunc(x) if (x<0) disp('error') return disp(sqrt(x)) >> myfunc(1) 1 >> myfunc(5) ü x ü x 0 x >> myfunc(-1) error 54

55 input Input MATLAB Enter MATLAB 55

56 input >> age=input('please enter your age: ') Please enter your age: 18 age = 18 >> name=input('what is your name: ', 's') What is your name: Jim name = Jim 56

57 pause pause: pause(n): n 57

58 continue continue for while continue for while 58

59 continue for i=1:5 if (i==3) continue disp(i) ,2,,5 3 59

60 continue for i=1:5 disp(i); continue; disp(i*i); ü continue 60

61 break break for while break 61

62 break limit = 0.9; while 1 tmp = rand; disp(tmp); if tmp > limit break

63 break for i=2:10 prime=1; for j=2:floor(sqrt(i)) if(~mod(i,j)) prime = 0; break; if(prime == 1) fprintf('%d is prime\n', i); 2 is prime 3 is prime 5 is prime 7 is prime 10 63

64 64

65 MATLAB for while M M M M : tic & toc toc tic p156-p157 65

66 A=rand(1000); B=rand(1000); tic C=A*B; toc A=rand(1000); B=rand(1000); C=zeros(1000, 1000); tic for i=1:1000 for j=1:1000 C(i, j)=dot(a(i, :), B(:, j)); toc Elapsed time is seconds. Elapsed time is seconds. 66

67 whos clear clear varname varname clear >> a=1; >> b=2; >> whos Name Size Bytes Class Attributes a 1x1 8 double b 1x1 8 double >> clear a; >> whos Name Size Bytes Class Attributes b 1x1 8 double 67

68 save save filename filename save filename x y z x y z filename load load filename filename mat load filename x y z filename mat x y z 68

69 save load datafile 69

70 save load 70

71 save load datafile b 71

72 save load datafile 72

73 73

74 Thank You! 74