[BUG] nan value when complexity measure is calculated

[Yeoonsu]

Describe the bug
Hello. It's the first time to write 'Issues' tab. (I'm a fresh github user)
If I'm not proper in github format and English writing, please understand.

The problem is,
when I calculate complexity measure, I usually get 'nan' value randomly. I have been through a few weeks, and read the code with some papers, but I can't guess why.
I replace the nan value with 0, but I'm worried there's no exact logic for me.
what is the difference between nan and 0.0? Do you think is it okay to this replacement(nan to 0)?

Could you give me any advice?
Thank you.

Screenshots
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Additional context
Thank you for creating pymfe. It is big helpful to my first research.

[FelSiq]

Hi @Yeoonsu, thanks for your feedback.

When "NaN" values are generated, it typically occurs when either meta-feature extraction methods or summary functions fail to compute. In your case, it appears that the standard deviation (sd) returned "NaN" because there was only a single value available for calculation, since the mean values appear to be all valid. This behavior is expected and not considered a bug.

It is difficult to tell you what you should do, because the preferable approach might depends on the nature of your analysis. You can set the missing values to an obvious invalid value (e.g. -1.0 to the standard deviation), or fill it using mean/median values from other datasets. Each method for filling missing data has its advantages and downsides, and there is no universally "correct" answer.

[FelSiq]

I'm closing this issue. Please fell free to reopen it if necessary.

Best regards,
Felipe.