Flow control
Flow control
Conditionals
(& the 2 brothers problem)
Conditionals
if
condition
do this stuff
end
if
condition
do this stuff
else
do this stuff
end
if
condition
do this stuff
elseif
condition
do this stuff
else
do this stuff
end
Conditionals
if
condition
do this stuff
end
condition
should evaluate to
logical
true or false
. examples:
x > 5
y == 5
x<3 & y>=7
strcmp(subject,’S01’)
Flow Control (IF statement)
d=10;
if d<5
'less than 5'
else
'not less than 5'
end
output?
d=10
True?
no
Skip to
here
end
•
The
if
statement evaluates a logical expression and executes a group of
statements when the expression is
TRUE
. The optional
elseif
and
else
keywords provide for the execution of alternate groups of statements. An
end
keyword, terminates the last group of statements
•
Example: for different values of A
If (A > B)
% Test for condition A > B
disp('A is greater than B'); % disp writes string argument to screenelseif (A < B) % Test for condition A < B
disp('A is less than B');elseif (A == B) % Note that == means test for equality
disp('A and B are equal');else
disp('Rather unexpected situation.... ')end
Flow Control (IF statement)
•
The
if
statement evaluates a logical expression and executes a group of
statements when the expression is TRUE. The optional
elseif
and
else
keywords provide for the execution of alternate groups of statements. An
end
keyword, terminates the last group of statements
•
Example: for different values of A
If (A > B)
% Test for condition A > B
disp('A is greater than B'); % disp writes string argument to screenelseif (A < B) % Test for condition A < B
disp('A is less than B');elseif (A == B) % Note that == means test for equality
disp('A and B are equal');else
disp('Rather unexpected situation.... ')end
function
isItBigger(x,y)
% will decide if x is bigger than y
if
x > y
fprintf(
'Yes, x is bigger than y.\n'
);
else
fprintf(
'No, x is not bigger than y.\n'
);
end
>>
isItBigger(3,4)
No, x is not bigger than y.
>>
isItBigger(8,4)
Yes, x is bigger than y.
function
isItNine(x)
% will decide if x is equal to 9
if
x = 9
fprintf(
’It is nine!\n'
);
else
fprintf(
'No, its not nine.\n'
);
end
function
isItNine(x)
% will decide if x is equal to 9
if
x == 9
fprintf(
’It is nine!\n'
);
else
fprintf(
'No, its not nine.\n'
);
end
function
fruit =
pickAFruit(color,size)
% choose a fruit based on color and size
% color is a string, and size is a double representing weight in grams
if
strcmp(color,
’red
’)
if
size < 10
fruit =
‘apple’
;
else
fruit =
‘watermelon’
;
end
elseif
strcmp(color,
’yellow’
)
fruit =
‘banana’
;
else
fruit =
‘unknown’
;
end
Nested conditionals
Switch and Case Statements
•
The
switch
statement executes one of a group of
case
statements, based on whether the value of a
variable (logicals included) is the same in both. Only
the first match is executed. If no match is found,
otherwise
is executed.
•
% In this example, need first to specify a
positive integer value for n
switch (rem(n,2)) % use help “rem”
case 0
disp('n is even');case 1
disp('n is odd')otherwise
error('This seems hard to believe')end
Useful videos
•
https://www.youtube.com/watch?v=rzm_FyZ9SmA
(Selection (Branching) in MATLAB - 12min)
•
https://www.youtube.com/watch?v=rEarTHsM5dY
(If-Statement cont'd – 8min)
•
https://www.youtube.com/watch?v=vJpeMFfwpTM
(Nested If-statements – 2min)
Diving into flow control and conditionals in programming, this content discusses various concepts such as if statements, logical evaluations, and nested conditionals. Explore examples and practical implementations to enhance your understanding of how to control the flow of a program based on conditions.
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Presentation Transcript
Conditionals (& the 2 brothers problem)
Conditionals if condition if condition if condition do this stuff do this stuff do this stuff end elseif condition else do this stuff do this stuff else end do this stuff end
Conditionals condition should evaluate to logical true or false. examples: x > 5 y == 5 x<3 & y>=7 strcmp(subject, S01 ) if condition end do this stuff
Flow Control (IF statement) d=10; d=10 if d<5 'less than 5' else 'not less than 5' end True? no Skip to here output? end
Flow Control (IF statement) The if statement evaluates a logical expression and executes a group of statements when the expression is TRUE. The optional elseif and else keywords provide for the execution of alternate groups of statements. An end keyword, terminates the last group of statements end keyword, terminates the last group of statements The if statement evaluates a logical expression and executes a group of statements when the expression is TRUE. The optional elseif and else keywords provide for the execution of alternate groups of statements. An Example: for different values of A If (A > B) disp('A is greater than B'); % disp writes string argument to screen elseif (A < B) % Test for condition A < B disp('A is less than B'); elseif (A == B) % Note that == means test for equality disp('A and B are equal'); else disp('Rather unexpected situation.... ') end end Example: for different values of A If (A > B) % Test for condition A > B % Test for condition A > B disp('A is greater than B'); % disp writes string argument to screen elseif (A < B) % Test for condition A < B disp('A is less than B'); elseif (A == B) % Note that == means test for equality disp('A and B are equal'); else disp('Rather unexpected situation.... ')
function isItBigger(x,y) % will decide if x is bigger than y if x > y fprintf('Yes, x is bigger than y.\n'); else fprintf('No, x is not bigger than y.\n'); end >> isItBigger(3,4) No, x is not bigger than y. >> isItBigger(8,4) Yes, x is bigger than y. function isItNine(x) % will decide if x is equal to 9 if x = 9 fprintf( It is nine!\n'); else fprintf('No, its not nine.\n'); end function isItNine(x) % will decide if x is equal to 9 if x == 9 fprintf( It is nine!\n'); else fprintf('No, its not nine.\n'); end
Nested conditionals function fruit = pickAFruit(color,size) % choose a fruit based on color and size % color is a string, and size is a double representing weight in grams if strcmp(color, red ) if size < 10 else end fruit = apple ; fruit = watermelon ; elseif strcmp(color, yellow ) fruit = banana ; else fruit = unknown ; end
Switch and Case Statements The switch statement executes one of a group of case statements, based on whether the value of a variable (logicals included) is the same in both. Only the first match is executed. If no match is found, otherwise is executed. % In this example, need first to specify a positive integer value for n switch (rem(n,2)) % use help rem case 0 disp('n is even'); case 1 disp('n is odd') otherwise error('This seems hard to believe') end
Useful videos https://www.youtube.com/watch?v=rzm_FyZ9SmA (Selection (Branching) in MATLAB - 12min) https://www.youtube.com/watch?v=rEarTHsM5dY (If-Statement cont'd 8min) https://www.youtube.com/watch?v=vJpeMFfwpTM (Nested If-statements 2min)
