1. Introduction to Programming in MATLAB
Intro. MATLAB Peer Instruction Lecture Slides by Dr. Cynthia Lee, UCSD is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Based on a work at 

2. Conditional Statements
Note: display(arg) prints the value of arg back to you

3. Conditional Statements
function [ ] = PrintAgeInfo( age )
if (age >= 16)
display('Can drive');
end
if (age >= 18)
display('Can vote');
if (age >= 21)
display('Can drink');
if (age >= 65)
display('Can collect Social Security');
How many strings are printed when we type PrintAgeInfo(30) in the Command Window?
(a) (b) (c) (d) (e) 4 D
Prints “can drive” “can vote” and “can drink”

4. Conditional Statements
function [ ] = PrintAgeInfo( age )
if (age >= 16)
display('Can drive');
elseif (age >= 18)
display('Can vote');
elseif (age >= 21)
display('Can drink');
elseif (age >= 65)
display('Can collect Social Security');
end
When we type PrintAgeInfo(30) in the Command Window, is ‘Can vote’ printed?
(a) yes (b) no (c) I don’t know/Other
B – no.
Prints “can drive” but then goes to the end of the conditional statement without checking other tests, because one test has already been True.

5. Conditional Statements
function [ ] = HelloPuzzle( x )
if (x >= 3)
display(‘Hello!');
else
display(‘Hello!’);
if (x > 1)
end
How many strings are printed when we type HelloPuzzule(5) in the Command Window?
(a) (b) (c) (d) (e) I don’t know/Other B
5 >= 3 so that test passes and “Hello!” is printed. Even though the second condition in the code (5>1) is true, we do not even run that test because it is in the else clause of the first test, and is thus skipped. This is a really hard concept for students.

6. Review/check-up
You get a job at the DMV and your boss asks you to write a function IsDrivingAge as follows: (1) takes one argument, a number giving the age in years, and (2) returns true if the age is 16 or more and false otherwise.
Which of the following codes fulfills this request?
function [] =IsDrivingAge(age)
if (age >= 16)
display(‘true’);
else
display(‘false’);
end
function [y] =IsDrivingAge(age)
if (age >= 16)
display(‘true’);
y = true;
else
display(‘false’);
y = false;
end
This is really not an if/else question, it is a test to see if they understand the difference between displaying something and returning it. This is a REALLY common misunderstanding. C
This displays the answer, does not return it
This displays and returns. It is better than (a), but, generally, when you are given a function specification you should follow it exactly and not display things to the screen unless told to do so.
Correct—returns the desired value
NOT personal preference! (perhaps some leeway between B and C, but A is wrong) A
function [y] =IsDrivingAge(age)
if (age >= 16)
y = true;
else
y = false;
end B
Any of these is fine, it is just personal preference. D C