Lecture (03) Arrays. By: Dr. Ahmed ElShafee. Dr. Ahmed ElShafee, ACU : Spring 2018, HUM107 Introduction to Engineering

Transcription

1 Lecture (03) Arrays By: Dr. Ahmed ElShafee ١ Dr. Ahmed ElShafee, ACU : Spring 2018, HUM107 Introduction to Engineering Characters and Strings Strings are defined by delimiting text with single quotation marks: ٢

2 To make a single quote part of a string, you just type it twice As you can see, a string in our case is simply an array of eight characters ٣ You can, of course, access individual string characters The simplest way of joining strings together is to simply use square brackets around the parts to join: ٤

3 Note however that attempting to include numeric values into the concatenation can lead to unforeseen consequences, such as having your numeric value converted to a character symbol with the corresponding ASCII code ٥ The reverse is useful though: for example, to quickly get a line break between two lines of text, you can rely on MATLAB to convert the number 10 into the character code for a line break. Thus, adding a line break between two pieces of text is as simple as: ٦

4 To get numeric data in text form, simply use the num2str function ٧ use the disp function: ٨

5 Strings are used in many places. For example, to plot a graph of ٩ string comparison functions strcmp and strcmpi for casesensitive and insensitive comparisons ١٠

6 Structures Let s say that in our MATLAB program we need to store some data about a person, such as their name and age. We can certainly use two variables for this or, as an alternative, we can define a structure. ١١ And it may seem as though person is just one entity, but in actual fact, it's an array that has just one element. ١٢

7 ١٣ Cell Arrays if you consider structures as entities whose fields are addressable via their names, then cell arrays are that same idea, but the elements are kept in an array, and are addressable by position. Let us define that same student entity we met previously, but using a cell array instead: ١٤

8 ١٥ If you want to get the actual value, instead of using round parentheses, you use curly braces, so writing student{1} ١٦

9 Function Handles A function handle is a variable, but instead of storing a numeric or textual value, it actually points to a different function For example, you can define a variable that points to the sin function and then use it for invocation. ١٧ ١٨

10 ١٩ Mathematical Operations with Arrays Element by element operations: ADDITION AND SUBTRACTION ٢٠

11 ٢١ ٢٢

12 ٢٣ ARRAY MULTIPLICATION ٢٤

13 ٢٥ ٢٦

14 ٢٧ ٢٨

15 ٢٩ ٣٠

16 ARRAY DIVISION Identity matrix: eye command ٣١ Inverse of a matrix: ٣٢

17 ٣٣ ٣٤

18 Determinants: ٣٥ Array division: MATLAB has two types of array division, right division and left division. Left division, \: Right division, /: ٣٦

19 Example 01 Solving three linear equations (array division) ٣٧ ٣٨

20 ٣٩ BUILT IN FUNCTIONS FOR ANALyZING ARRAYS ٤٠

21 ٤١ Example 02 (Friction experiment (element byelement calculations) ٤٢

22 ٤٣ Example 03, Electrical resistive network analysis (solving a system of linear equations) Consider that the voltage drop over a closed loop: ٤٤

23 ٤٥ ٤٦

24 ٤٧ Example 04: Motion of two particles 200 ft create an 11 x 6 matrix in which each row has the time in the ftrst column and the train position, car position, distance between the train and the car, car speed, and the speed of the train relative to the car in the next ftve columns, respectively. 400 ft The position of an object that moves along a straight line at a constant acceleration is given by The car is accelerating and its velocity at time tis given by ٤٨

25 200 ft The velocity of the train relative to the car, vt/c, is given by: 400 ft ٤٩ 1 / / ٥٠

26 ٥١ Thanks,.. ٥٢ Dr. Ahmed ElShafee, ACU : Spring 2018, HUM107 Introduction to Engineering