[jira] [Comment Edited] (ARROW-13364) [C++] Should NaN comparison return false or NaN/NA?

["Eduardo Ponce (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-13364?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17382453#comment-17382453 ] 

Eduardo Ponce edited comment on ARROW-13364 at 7/17/21, 4:44 AM:
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R uses *NA* to represent a missing value, equivalent to having a *NULL* bit set in Arrow.

Coercing NaN to logical or integer type gives an NA of the appropriate type, but coercion to character gives the string "NaN". NaN values are incomparable so tests of equality or collation involving NaN will result in NA.

w.r.t. R's behavior for
{code:r}
> NaN > 5
[1] NA
{code}
it does not seems to conform strictly to IEEE 754. My speculation is that internally the result is *NaN* but when coerced as a logical type becomes *NA*.

 


was (Author: edponce):
R uses *NA* to represent a missing value, equivalent to having a *NULL* bit set in Arrow.

Coercing NaN to logical or integer type gives an NA of the appropriate type, but coercion to character gives the string "NaN". NaN values are incomparable so tests of equality or collation involving NaN will result in NA.

w.r.t. R's behavior for
{code:R}
> NaN > 5
[1] NA
{code}
it does not conforms to IEEE 754. My speculation is that internally the result is *NaN* but when coerced as a logical type becomes *NA*.



 

> [C++] Should NaN comparison return false or NaN/NA?
> ---------------------------------------------------
>
>                 Key: ARROW-13364
>                 URL: https://issues.apache.org/jira/browse/ARROW-13364
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: C++
>            Reporter: Jonathan Keane
>            Priority: Major
>
> In working on ARROW-12964 we ran into some corner behaviors with {{NaN}} that don't match our (and R's) expectations. It appears that (any?) comparison with `NaN` results in false:
> {code:r}
> > Scalar$create(NaN) > 5
> Scalar
> false
> {code} 
> though at least in R this would result in an NA value:
> {code:r}
> > NaN > 5
> [1] NA
> {code}
> The current behavior _does_ match numpy's behavior:
> {code:python}
> >>> np.nan > 5
> False
> {code}



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