community
cancel
Showing results for 
Search instead for 
Did you mean: 

Alteryx designer Discussions

Find answers, ask questions, and share expertise about Alteryx Designer.

Correlation output contains null (not running correlation with nulls)

Hello!  First post on the community board, so I appreciate your patience.

 

I've recently run a correlation analysis using the Pearson tool and the outputs contained nulls.  The field type is float for all fields and all nulls have been converted to zeros.  We would suspect if there was no correlation, the output would say "0" rather than Null.  

 

Has anyone else seen this before?  If so, can anyone share what the fix is for this? 

 

Thanks in advance!

Highlighted
Alteryx Certified Partner
Alteryx Certified Partner

Hi @brittanylutz

 

Could you please share your workflow, or at least the data which was streamed to the Pearson Tool?

 

Cheers,

Unfortunately, no, the data is confidential.  Are you able to explain if there are certain criteria that must be met for a correlation to be calculated (i.e. is it possible if 95% of the records within a field are 0, then correlation can't be calculated and therefore returns Null)

Alteryx Certified Partner
Alteryx Certified Partner

@brittanylutz 
It's hard to tell why.

I know the pearson coefficient is the covariance of two variables divided by the product of their standard deviations.

Maybe if the standard deviation is = 0, but you said there's data different than 0, I assume that does not happen.

 

Did you try to calculate it in some other software?

Thanks so much for your help; I checked again and believe now that it was because the standard deviation was 0.

Labels