1. CS005 Introduction to Programming:
Matlab
Eamonn Keogh

2. Let us write a function called IsOdd, that takes in an integer, and returns true (‘1’) if it is odd, otherwise returns a false (‘0’). 2 7
IsOdd
IsOdd 1

3. Here are some basic facts we can exploit:
EDU>> (7/2)
ans =
3.5000
EDU>> (11/2)
5.5000
EDU>> (4/2) 2
EDU>> (18/2) 9
When I divide an odd number by 2, the answer is always “something.5000”.
This is not the case for even numbers, they never have a fractional part.

4. Here are some basic facts we can exploit:
EDU>> (7/2)
ans =
3.5000
EDU>> (11/2)
5.5000
EDU>> (4/2) 2
EDU>> (18/2) 9
EDU>> floor(7/2)
ans = 3
EDU>> floor(11/2) 5
EDU>> floor(4/2) 2
EDU>> floor(18/2) 9
When I take the floor of a odd number divided by 2, the answer is always 0.5 smaller….
This is not the case for even numbers.

5. function WasOdd = IsOdd(IntegerToTest)
if IntegerToTest/2 > floor(IntegerToTest/2)
WasOdd = 1;
else
WasOdd = 0;
end

6. function WasOdd = IsOdd(IntegerToTest)
if IntegerToTest/2 > floor(IntegerToTest/2)
WasOdd = 1;
else
WasOdd = 0;
end
EDU>> (7/2)
ans =
3.5000
EDU>> floor(7/2) 3

7. function WasOdd = IsOdd(IntegerToTest)
if IntegerToTest/2 > floor(IntegerToTest/2)
WasOdd = 1;
else
WasOdd = 0;
end
EDU>> (4/2)
ans = 2
EDU>> floor(4/2)

8. Iteration (looping) true false The for statement Get the Users Score
Run some code multiple times
Check for condition
true
Process code
false
Jump to end…

9. We can repeat a code block multiple times with the for statement
for index = values
do these statements
end

10. for i = 1 : 10 do these statements end Start with i at this value
Stop when i hits this value
for i = 1 : 10
do these statements
end
Make i one larger when you get here

11. function DummyVar = SaySpamFiveTimes for i = 1 : 5 disp('Spam') end
EDU>> SaySpamFiveTimes
Spam
EDU>>

12. function DummyVar = SaySpam(TimesToRepeat) for i = 1 : TimesToRepeat
disp('Spam')
end
EDU>> SaySpam(2)
Spam
EDU>> SaySpam(0)
EDU>> SaySpam(4)
EDU>> SaySpam(50)
Spam (I deleted the rest, eamonnn)

13. function DummyVar = CountToTen() for i = 1 : 10 disp(i) end
EDU>> CountToTen 1 2 3 4 5 6 7 8 9 10
EDU>>

14. function DummyVar = CountToK(K) for i = 1 : K disp(i) end
EDU>> CountToK(4) 1 2 3 4
EDU>> CountToK(0)
EDU>> CountToK(2)
EDU>>

15. function DummyVar = CountFromKuptoL(K,L) for i = K : L disp(i) end
EDU>> CountFromKuptoL(3,7) 3 4 5 6 7
EDU>> CountFromKuptoL(99,104) 99
100
101
102
103
104
EDU>>

16. function DummyVar = SevenTimesTable() for i = 1 : 10
disp('Seven times ');
disp(i);
disp(' is ');
disp(i * 7);
end
>> SevenTimesTable
Seven times 1 is 7 2 14 3 21
(I deleted the rest, eamonn)

17. Let us write a function called GetTriangularNumber, that takes in an integer T, and returns the Tth triangular number. 2
GetTriangularNumber 3

18. function DummyVar = CountToK(K)
% We saw this function a few slides ago..
for i = 1 : K
disp(i)
end
EDU>> CountToK(6) 1 2 3 4 5 6
EDU>>
So, we know how to print out all the integers from 1 to 6, if we could just add them up as we printed them, it would solve our problem, so:
Let us work by adapting a working function that does something similar.

19. function DummyVar = CountToK(K)
% We saw this function a few slides ago..
for i = 1 : K
disp(i)
end
Let us work by adapting a working function that does something similar.
Rename the function
Pass in T, the order of the triangular number
Return the actual triangular number
(we have more to do, next slide)
function TriangularNumber = GetTriangularNumber(T)
for i = 1 : T
disp(i)
end

20. function TriangularNumber = GetTriangularNumber(T)
for i = 1 : T
disp(i)
end
function TriangularNumber = GetTriangularNumber(T)
TriangularNumber = 0;
for i = 1 : T
TriangularNumber = TriangularNumber + i;
end

21. EDU>> GetTriangularNumber(17) ans = 153 EDU>>
When they landed, they saw a fire of burning coals there with fish on it, and some bread. Jesus said to them, "Bring some of the fish you have just caught."  Simon Peter climbed aboard and dragged the net ashore. It was full of large fish, 153, but even with so many the net was not torn. Jesus said to them, "Come and have breakfast." None of the disciples dared ask him, "Who are you?

22. function TriangularNumber = GetTriangularNumber(T)
% We can add some error checking
if T < 0
disp('Error: Triangular Numbers are only defined for positive numbers')
end
TriangularNumber = 0;
for i = 1 : T
TriangularNumber = TriangularNumber + i;
EDU>> GetTriangularNumber(2)
ans = 3
EDU>> GetTriangularNumber(-3)
Error: Triangular Numbers are only defined for positive numbers
EDU>>

23. function TriangularNumber = GetTriangularNumber(T)
% Nesting the for loop inside the else block is better
if T < 0
disp('Error: Triangular Numbers are only defined for positive numbers')
else
TriangularNumber = 0;
for i = 1 : T
TriangularNumber = TriangularNumber + i;
end
EDU>> GetTriangularNumber(2)
ans = 3
EDU>> GetTriangularNumber(-3)
Error: Triangular Numbers are only defined for positive numbers
EDU>>