> On 19 Aug 2019, at 15:45, akash srivastava <akashsp...@gmail.com> wrote:
>
> I was advised to check with the dev mailing list if anyone has a problem
> with the suggested fix.
> It seems no one does have a problem with the fixes suggested so I'll go
> forward and create a PR that returns an empty array for an array of all
> NaNs.
I suggested doing the same as what happens when you pass in an empty array,
effectively changing the array of NaNs to an array of nothing.
Reading the code it appears that this case would throw an
ArrayIndexOutOfBoundsException. A simple test case shows that this is true,
e.g. this passes:
@Test(expected=ArrayIndexOutOfBoundsException.class)
public void testEmpty() {
new NaturalRanking().rank(new double[0]);
}
So the fix for rank() on an array of NaNs has no equivalent with a normal array
as an empty normal array is an edge case currently not handled.
IMO returning an empty array is not going to be useful. If someone is using
this class to rank data then immediately after ranking I would assume they will
use the rank to do something, e.g. pick the top one. An empty array will fail
for most use cases I can think of since they will require dereferencing the
rank array. Only if the array is used without dereferencing it, e.g. print to
file, or if the size of the rank array is checked before using the contents
will an empty array be OK.
So the question becomes which is better:
- Returning an empty array and requiring users to check its length or else
receive ArrayIndexOutOfBoundsException when using the array contents
- Throwing an exception so that the exact cause of their bug can be recorded in
the stack trace
I would suggest that an array of NaNs or an empty array should throw the same
and it should be some sort of IllegalArgumentException. Currently this class
only throws NotANumberException for errors. Perhaps for these two cases an
math4.exception.InsufficientDataException should be thrown. This basically
states that you cannot rank nothing and any result that is returned will
contain a ranking.
Opinions?
>
> On Thu, Aug 15, 2019 at 11:25 AM akash srivastava <akashsp...@gmail.com>
> wrote:
>
>> Here is the link for the related bug:
>> https://issues.apache.org/jira/browse/MATH-1495
>>
>> I have suggested two possible fixes when NaturalRanking#rank() is called
>> on an array of all NaNs:
>> 1) throwing an IllegalArgumentException
>> 2) Returning an empty array
>>
>> I want to create a pull request regarding it, which fix do you suggest I
>> should go for?
>>
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