1 / 25

MATLAB Scripting Techniques Lecture

Learn to create scripts, functions, and manipulate variables in MATLAB for efficient programming. Practice examples included.

gertrudeg
Download Presentation

MATLAB Scripting Techniques Lecture

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Lecture 7 Sept 17 • Goals: • Complete Chapter 4 • Chapters 5 and 6

  2. Scripts • Sequence of instructions that we may want to run can be stored in a file (known as script). • by typing the name of the file, Matlab executes the sequence of operations. • files can be created by any plain text editor (such as notepad) or the editor that comes with Matlab. • Example:

  3. Files, path, working directory etc. • We can save the values of the current variables using the save command. • >> save(‘temp’, ‘a’, ‘b’, ‘c’); • Will save variables a, b, c in temp. • default directory is named work. But this can be changed by specifying other paths. • Example:

  4. Files, path, working directory etc. • We can load a file using the load command. • Example:

  5. Importing and exporting data We can read from an Excel spreadsheet using the command: >> tab = xlsread(‘my_file.xls’); Now tab becomes a matrix. Example:

  6. Reading a plain text ASCII file

  7. Functions • functions encapsulate computations that are repeatedly performed. • input and output parameters. • Example 1: Write a function to compute the hypotenuse of a right triangle given the two smaller sides a a and b.

  8. function c = hyp(a, b) • c = sqrt(a*a + b * b); • This file should be stored in the current directory that is visible to Matlab. • Then we can perform: • >> hyp(3, 4) • ans = • 5

  9. Example 2: Write a function swap that takes as input an array of integers and returns an array by swapping the max key and the key in index 1. For example: >> B = [1, 2, 8, 4, 7, 5, 6]; >> C = swap(B); >> C Ans = [8, 2, 1, 4, 7, 5, 6]; Etc.

  10. Function swap function B = swap (A) [temp, id] = max(A); A(1) = A(1)+ A(id); A(id)= A(1) - A(id); A(1) = A(1) - A(id); B = A;

  11. Local vs. global variables

  12. Example 3: Write a function GCD that outputs the greatest common divisor of two positive integers n and m. Recall Euclid’s algorithm: GCD of 52 , 9 compute mod(52, 9) = 7 new pair: 9, 7 mod(9, 7) = 2 7, 2 mod(7, 2) = 1 2, 1 mod(2, 1) = 0 1, 0 When we reach pair (x, 0), x is the GCD.

  13. GCD function • We need to know how to create a loop. There are two ways to do this: • for loop • while loop • For this problem, we will use the while loop.

  14. GCD function function m = gcd(a, b) while ~(b==0) rem = mod(a, b); a = b; b = rem; end; m = a;

  15. Exercise: Write a function that takes as input a positive integer n and returns the first prime number greater than n. Recall the function isprime in Matlab that returns true (false) if the input is a prime (is not a prime).

  16. Exercise: Write a function that takes as input a positive integer n and returns the first prime number greater than n. • Recall the function isprime in Matlab that returns true (false) if the input is a prime (is not a prime). • function n = nextPrime(m) • n = m + 1 • while 1 • if isprime(n) break; • else n = n + 1; • end; • end;

  17. Exercise 6.1: Write a function, powersum, that computes for any specified values of z and n.

  18. Exercise 6.1: Write a function, powersum, that computes for any specified values of z and n. Solution:

  19. Exercise 6.2 (d) Write a function eliminate that takes as input a character string and returns a string of the same length in which e and E have been replaced by *. Hint: Use find and the index operator. Example: >> eliminate(‘TherE’) ans = Th*r*

  20. Exercise 6.2 (d) Write a function eliminatethat takes as input a character string and returns a string of the same length in which e and E have been replaced by *. Hint: Use find and the index operator. Solution:

  21. Exercise 6.3: function out = addToEnd(a, x) out = [a, x]; Just calling the function with a as argument does not change its value. a = addToEnd(a, x) will change a as desired.

  22. Exercise 6.6 >> BooleanToTF([1 0 0 1 1 0 1 0]) ans = ‘TFFTTFTF’ etc.

  23. Exercise 6.6 >> BooleanToTF([1 0 0 1 1 0 1 0]) ans = ‘TFFTTFTF’ etc. function res = BooleanToTF(bool) res = char('F' + zeros(size(bool))); res(bool) = 'T';

  24. Exercise: write a function in Matlab to convert from decimal to binary. The output should be a string.

  25. Exercise: write a function in Matlab to convert from decimal to binary. The output should be a string. function bin = dec2bin(n) if n == 0 bin = '0'; else bin= ''; while ~(n==0) if mod(n,2)==0 bit = '0' else bit = '1'; end; bin= strcat(bin, bit); n = floor(n/2); end; end;

More Related