1. Introduction to Programming for Mechanical Engineers (ME 319)
Lecture 6.2

2. Things you should have known so far!
If you didn’t have it before, you should have developed some knowledge of logic design. True-False or 0-1 representation
Understand the nature of logical and relational operators.
Clearly forming logical and relational operators to represent the case(s) you may have.
Correctly arrange combined conditions to represent more complex case(s).

3. Conditional Statements: if-end
Conditional statements are statements designed to allow MATLAB to make decision making. Here, the MATLAB may execute a group of commands or skip them based on the satisfaction of a condition(s).
Syntax:
if conditional expression(s), logical and relational
body of ‘if’ statement
end
START
IF STATEMENT
FALSE
TRUE
Group of commands
Example:
if n_boys>=0
n_students = n_girls + n_boys;
end
END

4. Conditional Statements: if-else-end
If-else-end is a two way conditional statement. The statement checks the satisfaction of the condition. If it is satisfied, it chooses command group 1 and executes it.
If the condition is false, it chooses group 2 and executes it.
START
IF STATEMENT
FALSE
TRUE
Example:
if GPA>=3.0
DECISION = ‘PASS'
else
DECISION = ‘FAIL'
end
Group of commands 2
Group of commands 1
END

5. Conditional Statements: if-elseif-end
If-elseif-end is a multi way conditional statement. The statement checks the satisfaction of the first condition. If it is satisfied, it chooses commands group 1 and executes it. If the condition is false, it goes to the second else-if statement. It performs the same check to choose group 2 or 3.
START
IF STATEMENT
FALSE
Example:
if GPA>=3.75
EVALUATION = ‘A'
elseif GPA<3.75 & GPA>=3.50
EVALUATION = ‘B+'
else % GPA<3.50 & GPA>=3.20
EVALUATION = ‘B‘
end
ELSE-IF STATEMENT
TRUE
FALSE
Group of commands 1
TRUE
Group of commands 3
Group of commands 2
END

6. .. Conditional Statements: switch-case-otherwise-end
switch-case-otherwise-end is a conditional statement that works in parallel. Only one case is selected and the commands that follow it will be executed.
START
switch ..
otherwise
case value 3
case value 2
case value 1
END

7. Conditional Statements: switch-case-otherwise-end
passengers = input('Enter number of passengers ');
passengers = ceil(passengers);
switch passengers
case 1
Car_type = 'Coupe'
Rate_per_day_USD = 27
case 2
case 3
Car_type = 'Economy'
Rate_per_day_USD = 22
case 4
Car_type = 'Sedan'
Rate_per_day_USD = 25
case 5
Car_type = 'Full Size'
Rate_per_day_USD = 40
case 6
Car_type = 'Minivan'
Rate_per_day_USD = 57
otherwise
fprintf('We do not hold cars that fit this number of passengers\n\n')
end
Enter number of passengers 5
Car_type =
Full Size
Rate_per_day_USD =
40.00

8. Thank you for the attention
Any Questions and Suggestions please…