1. Chapter 1-3 – Matlab Overview
ENGR 1320

2. Variables A symbol used to contain a value
Used to write mathematical expressions
Variable naming convention
Must begin with a letter
Must contain < 32 characters
Is case sensitive
May contain letters, digits, & underscore
Scalar variable - a single number
Array variable - a collection of numbers
Can be handled by MATLAB as a single variable

3. Variables Assigning values to variables Use “=“ as assignment operator
Variable name on left-hand side is replaced by value generated by right-hand side
Right-hand side must have computable value
Array assignment
“[]” contains numbers being assigned
Commas separate elements in row
Semi-colons separate rows
One and only one variable name is allowed on the left hand side of the assignment operator

4. Variables Array assignment (cont)
Special format for assigning row array with regularly spaced numbers
Type first number, last number, with spacing in middle
All numbers separated by colon “:”
One and only one variable name is allowed on the left hand side of the assignment operator

5. Variables Array addressing Use just variable name in expressions
Operation is performed on every element in the array
IF matrix operation is “legal”
Use variable name & array index in expressions
Point to a particular element in the array
Use if operation to be performed is not “legal” matrix operation
One and only one variable name is allowed on the left hand side of the assignment operator

6. Variables MATLAB has predefined variables
Avoid using names of predefined variables as variable names

7. Mathematical Expressions
Order of precedence
Highest order of precedence first
Operators of equal precedence from left to right

8. Functions MATLAB mathematical functions
Pair of parentheses after function name encloses function’s argument
Can be part of mathematical expression
There is an extensive list of functions in Chapter 3
Or you can use the online help

9. Functions Users can define functions
MATLAB commands and functions for managing the work session
There is an extensive list of functions in Chapter 3
Or you can use the online help

10. Plotting
Graphics window
Appears in Desktop when a plot is generated

11. Plotting Simple rectilinear plot Function plot(x,y)
Generates a plot with x-values on the horizontal axis and y-values on the vertical axis
Function xlabel(‘xxxx’)
Places text within single quotes as label for horizontal axis
Function ylabel(‘yyyy’)
Places text within single quotes as label for vertical axis
Functions are all written on same command line, separated by commas

12. Plotting Simple rectilinear plot (cont) Function title(‘text’)
Places text at top of plot
Overlay plots
Include another set or sets of values in plot function

13. Script Files Program files saved with .m extension Use Editor window
In Command window, select File, New, M-file
This opens editor window
When finished, select File, Save from Editor window

14. Script Files Naming convention Same as for naming variables
Not the same name as a variable or a MATLAB function
Use exist(‘name’) function to verify that a prospective filename is not already in use

15. Script Files Comments “%” - Not executed by MATLAB
Comments section – at beginning of program
1st line - name of the program, keywords
2nd line - date created and programmer’s name
3rd line – description of program’s purpose
Variable definitions
Input
Output
Internal to program
Include units for each variable, if applicable.

16. Script Files Comments Programming in MATLAB
Additional comments throughout program
Break program into sections.
Describe purpose for calculations
Programming in MATLAB
Relational operators
Used to make comparisons
Relational operators not needed for the first assignment

17. Script Files Programming in MATLAB (cont) Conditional statements
Allow decision-making
if expression
commands
elseif expression
else
end
Syntax for conditional statements and looping statements are case sensitive

18. Script Files Programming in MATLAB (cont) Loops Repeated calculations
For  Number of passes is known ahead of time
While  Looping terminates when a condition is met
for k=1:10
commands
end
while condition
commands
end
Syntax for conditional statements and looping statements are case sensitive
You will need to use a looping statement because you will not be able to do simple matrix calculations when you are calculating the material properties

19. Class Exercise Do the following in the Command Window:
>>clc
>>30/10
>>r = 30/10
>>r
>> s = 10*r
>>v = sin(s)
>>clear r
>>s
>>r = s
>>r = 10;
>>clear
>>help elfun
>>help sin
>>lookfor sine
Write an m-file script that performs the following calculation:
𝑓 𝑥 = 𝑥 2 cos⁡(2𝑥+1) 6𝑥 log⁡(𝑥)
Syntax for conditional statements and looping statements are case sensitive
You will need to use a looping statement because you will not be able to do simple matrix calculations when you are calculating the material properties