Pearson's r with no variation in data

Asked Jun 07 '17 at 08:50

Active Jun 07 '17 at 08:50

Viewed 23 times

I'm calculating Pearson's r for a set of dichotomous values.

For one item in my data set, all values are identical. Since the variance in y will be 0, I will ultimately end up with a division by 0.

I guess I have two questions:

Is it fair to say that the correlation coefficient is 0, or is it more valid to say that it cannot be calculated for this item?
Is manually checking for 0 variance and treating this as an exception the accepted best practice, or can the formula be modified to cater to this scenario?

asked Jun 07 '17 at 08:50

dxh

I think we normally say it is undefined. – mdewey Jun 07 '17 at 08:55
@mdewey: Thanks. After searching for some time for a discussion like this, searching for pearson's r undefined gave me this identical discussion. Someone with proper privileges can vote to close this as a duplicate, I suppose. – dxh Jun 07 '17 at 09:00
Thanks for the feedback, I have voted for closure as you suggest. – mdewey Jun 07 '17 at 09:04

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