checking input an integer greater than 0?

how can I check if my input is a integer greater than 0?

Answer 1

[John D'Errico]

If you want to check for an integer that exceeds zero, first use the && and || operators.

So assuming you want to throw an error if it fails, then I might do...

if (x <= 0) || (rem(x,1) ~= 0)
    error('Oh nO, Mr. Bill! x was not a positive integer.')
end

You use the || operator here, because MATLAB is more efficient with them in an if statement. They short circuit the test, so if the first part of the test is true, then there is no need to even execute the second clause in the test. The && operator works the same way.

I might even have added a test that x be a scalar variable.

If your question is you want to do something specifically if x is a positve integer, then another ay to write it would be:

if (numel(x) == 1) && (x > 0) && (fix(x,1) == 0)
    disp('Happy days are here again...')
else
    error('Oh nO, Mr. Bill! x was not a scalar positive integer.')
end

As you can see, I even added a test that x be scalar. There are of course alternative ways to test for an element being an integer. (fix(x)==x) is another, or (round(x) == x). Note that all such tests, when applied to a scalar are all extremely fast. Actually, the slowest of them is the rem test I used above.

You should also see that when I changed the if statement, I now had to use &&, which is the short-circuited version that applies.

[James Tursa]

Your first suggestion covers the x==inf case, but the second formulation doesn't.

[John D'Errico]

Good point. Best of course would be to explicitly test for inf or NaN input.

Answer 2

[Ameer Hamza]

You can use this condition

tf = (x>0) & (round(x)==x)

Example

>> x = 5;
>> tf = (x>0) & (round(x)==x)
tf =
  logical
   1
>> x = 4.5;
>> tf = (x>0) & (round(x)==x)
tf =
  logical
   0

[Jens Petit-jean]

Thanks but I need to use it with "if" before it but it doesn't work

[Ameer Hamza]

Can you give an example of how it does work?

[James Tursa]

Doesn't cover the x==inf case.

Answer 3

[Matt J]

validateattributes(yourInput,"numeric",{"integer","nonnegative"})

[John D'Errico]

"greater than 0"

validateattributes(yourInput,"numeric",{"integer","positive"})