MATLAB: Write a function, using arrays-vectors,’ input’& ‘fprintf’,’if’ statement’, ‘end’, ‘fgetl’ etc with good programming practices…like putting comments %

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*Task 3 [Intermediate] – 2 marks*
(a) Write a function that accepts a year as input and determines whether it is a leap year. The function should return 1 if the year is a leap year, otherwise return 0.
The rules for determining leap years are as follows:
1) All years evenly divisible by 400 are leap years
2) Years evenly divisible by 100 but not by 400 are NOT leap years
3) Years divisible by 4 but not 100 are leap years
4) All other years are NOT leap years
For example, 1800, 1900, 2100 are not leap years. 2000, 2004 and
2400 are leap years.
*HINT*: You may want to use the mod function and if statements
(b) Write a MATLAB program that asks the user for the month (1 to 12) and the year then prints the number of days in the month, taking leap years into account by reusing the function you wrote for part (a). For example, if the user enters 2 (February) and   2004 (leap year), the program should print 29.
*HINT*: You may want to try switch statements (help switch)

Best Answer

The formula given there for leap years is wrong, so it is not possible to write a correct leap year program based upon the given specifications.

http://www.perlmonks.org/?node_id=32583

Let's be precise: nowadays, your answer is right, but only since Gregorian reform, which has been take into account at different times in different countries. Before that, and since 45BC, there was a leap year in every year divisible by 4 (NOTE: 45BC is year -44).
Even that isn't exactly true... At the beginning people did not understand what "once in 4 years" meant, and there was a period (between 45BC and 9BC) where there was a leap year every 3 years. Followed by a period (between 8BC and 8AD) where there was no leapyear at all.

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The instructions ask for: "The output argument should be a Boolean variable". Your function IsLeapYear does not reply anything yet. This can be done by:

function T = IsLeapYear(Year)
T = ~mod(Year, 4) & (mod(Year, 100) | ~mod(Year, 400))
end

In the 2nd function think twice if this is correct:

m = endYear - startYear;

If endYear equals startYear, m is 0, but it should be 1.

You create v already, but do not use it, but it is a good solution:

for c = 1:m
    b(c) = IsLeapYear(v(c));
end

Now b is a logical vector, which is TRUE for the leap years. You can use it directly to reply the leap years only:

outputArg1 = v(b);

MATLAB: Function takes far too long to run, and then doesn’t write all the values to a text document.

Your code runs fine for me (and write all the entries to the file)

>>tic; GetLeapYears(0, 10000); toc;
Elapsed time is 0.055957 seconds.

So it must be a problem with your machine or location where you're writing the file.

Notwithstanding the speed issue, your code could substantially be improved.

In your GetLeapYears function, you sometimes use GetLY(n) sometimes GetLY(:, n). Be consistent!. Since GetLY is a row vector the colon is never needed.

Similarly, in your IsLeapYear function you sometimes use logical operations on logicals (e.g. (w_1 == 1) && (z_1 == 0)) and sometimes use arithmetic operations: elseif x_1+z_1==0. That latter expression is equivalent to elseif ~x_1 & ~x_2.

Also, since w_1 is logical , w_1 == 1 is the same as w_1 and z_1 == 0 is the same as ~z_1.

The main issue with your IsLeapYear function is that it can only operate on one year at a time, forcing you to use a loop in the other function. If you use simple boolean logic instead of if ... else, you can write a very simple IsLeapYear function that works on many dates at once, speeding up the code (which is already fast):

function LY = IsLeapYear(Y)
   LY = mod(Y, 400) & mod(Y, 100) & ~mod(Y, 4)
end

Best Answer

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MATLAB: MatLab multiple functions question

MATLAB: Function takes far too long to run, and then doesn’t write all the values to a text document.

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