How to test for integers and delete integers that do not perform to the test

My assignment: Write a function sumDiv5 which receives one input argument and returns how many elements of the input variable are divisible by 5. You are not allowed to use FOR loops (we will study them next week)

My thinking is to divide the whole input by 5. Then to delete all the non-integer numbers (those not divisible by 5). How do I delete only the non-integer numbers instead of the whole matrix? (which is what my code does)

function output= sumDiv5 (input)
A=input/5;
if isreal(A) && rem(A,1)==0
else 
    A=[];
end
output=A;

Answer 1

[Image Analyst]

Close. Study this snippet and see what you can learn:

data = randi(100, 1, 30)
divBy5 = rem(data, 5)

By the way, don't use "input" as a variable name because it's the name of a built-in function.

[Krish Desai]

This changes all the numbers divisible by 5 to 0. So I could delete all the non-zero terms and then add up the amount of 0's?

[Image Analyst]

No need to delete anything. Simply sum up the zeros:

count = sum(divBy5==0);

[Krish Desai]

Ok, I'm displaying the correct for when I have a vector, but when I try to input a matrix:

sumDiv5([0 1 2 3 4; 2 5 8 13 15]),

I get

1 1 0 0 1

Do I have to completely change the code, or is there a simple fix?

Current code:

function output= sumDiv5 (numbers)
A= rem(numbers,5);
count=sum(A==0);
output=count;

[Stephen23]

Try this:

function out = sumDiv5(mat)
out = sum(0==rem(mat(:),5));
end

And tested:

>> sumDiv5([0 1 2 3 4; 2 5 8 13 15])
ans =  3

Note that I also formatted the code in your question properly: in future please do this yourself by selecting the code text and clicking the {} Code button that you will find above the textbox.

Answer 2

[James Tursa]

Hint: Take a look at the result of rem(A,1)==0. What do you get if you sum this up?