• ENG 1181
College of EngineeringEngineering Education Innovation Center
P. 1
MAT - Conditional Statements
Topics Covered:
1. if based conditional statements.
if–end
if-else–end
if-elseif-else–end
2. switch-case
Programming in MATLAB / Chapter 6
• ENG 1181
P. 2
CONDITIONAL STATEMENTS
Conditional statements enable MATLAB to make
decisions.
The process is similar to the way we (humans)
make decisions.
A condition stated. If the condition is met, one set
of actions is taken. If the condition is not met, either
nothing is done, or a second set of actions is taken.Example:
If I win the Lottery,
•I will quit college, buy a new car, and go fishing.
If I do not win the Lottery,
•I will study harder so that I can get a better job.
174-179
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P. 3
THE FORM OF A CONDITIONAL STATEMENT
if a < b
if c >= 5
if a == b
if a ~= 0
if (d < h) & (x > 7)
if (x ~= 13) | (y < 0)
if Conditional expression
consisting of relational and/or logical operatorsExamples:
All variables must have assigned values.
174
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P. 4
FORMS OF THE if STATEMENT174-179
if conditional statement 1
command group 1
elseif conditional statement 2
command group 2
…
(Optional)elseif conditional statement # command group #
…
(Optional)
else %no conditional statement
command group n+1
end
if conditional statement
command group 1
else
command group 2
end
if conditional statement
command group
end
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P. 5
THE if–elseif-else-end STATEMENT
178-179
......
......if conditional expression
........
........
........elseif conditional expression
........
........
........else
........
........
........end......
Group 1 of MATLABcommands.
MATLAB program.
Group 2 of MATLABcommands.
Group 3 of MATLABcommands.
False
ElseIfconditional
True
False
TrueCommandGroup 1
End
Ifconditional
CommandGroup 2
CommandGroup 3
Examples of if-end and if-else-end can be found on pages 174-179 of the text
MATLAB program.
• ENG 1181
P. 6
• Bill less than $10• Tip is $1.80
• Bill between $10 and $60• Tip is %18
• Bill above $60• Tip is %20
USING THE if–elseif-else-end STATEMENTWrite program that calculates tip based on amount of bill, using the following rules
False
ElseIf$10 < bill < $60
True
False
Truetip = $1.80
End
Ifbill < $10
tip = bill * 0.18
tip = bill * 0.20
Else
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P. 7
USING THE if–elseif-else-end STATEMENT
% A script file that demonstrates the use of the % if-elseif-else-end statement.% The program calculates the tip in a restaurant % according to the amount of the bill.%% If the bill is less than $10 the tip is $1.80. % Between $10 and $60 the tip is 18% of the bill.% Above $60 the tip is 20% of the bill.
format bank
(The file continues on the next slide)
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P. 8
bill = input('Enter the amount of the bill (in dollars): ');
if (bill <= 10)
tip = 1.8;
elseif (bill > 10) & (bill <= 60)
tip = bill*0.18;
else
tip = bill*0.2;
end
disp('The tip is (in dollars):')
disp(tip)
USING THE if–elseif-else-end STATEMENT
Note how tip’s valueis control by ; and the disp command
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P. 9
>> Lecture8Example3Enter the amount of the bill (in dollars): 15The tip is (in dollars): 2.70
>> Lecture8Example3Enter the amount of the bill (in dollars): 6The tip is (in dollars): 1.80
>> Lecture8Example3Enter the amount of the bill (in dollars): 100The tip is (in dollars): 20.00
USING THE if–elseif-else-end STATEMENT
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P. 10
COMMENTS ABOUT if–end STATEMENTS For every if command must have an end command.
A program can have many if … end statements
following each other.
A computer program can perform the same task
using different combinations of if - end, if – else –
end, and if– elseif – else – end statements.
Multiple elseif conditions are allowed within an if–
elseif – else – end statement.
An else condition is not required.
When else is used, a conditional statement is
NOT added
174-179
• ENG 1181
P. 11
THE switch-case STATEMENT switch-case is similar to if-
elseif-end, except must be an exact match. You cannot use switch-case with a range, such as <0.
switch on scalar or string
otherwise == else(optional)
180- 184
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P. 12
THE switch-case STATEMENT
180- 184
x = input (‘Resistance: ‘);
switch x case 100
out= x; case 200
out= 2*x; case 300
out= 3*x; case 400
out= 4*x; otherwise
out = 0; end
• ENG 1181
P. 13
THE switch-case STATEMENT
180- 184
x = input (‘Purchase Class: ‘,’s’);x = upper(x) %change to upper case
switch x case ‘A’
rate = 2.00; case ‘B’
rate = 3.00; case ‘C’
rate = 3.50; case ‘D’
rate = 4.00; otherwise
rate = 0; end
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