Split: Refactor for discrete values, add tests, rename to "Text to Columns"

[janezd]

• Added tests for computation
• Changed treatment of nans for discrete values:
  • if value is nan, it doesn't mean it does not contain particular substrings, so newly created values must be nan.
  • This required too many changes wrt to string variables, so I created a separate class for one hot encoding of discrete values,
  • which are now computed faster (each distinct value is split only once and updated for all appearances),
  • so there is also need for shared computation because it only wastes memory.
• Renamed widget and modules.

Includes

• Code changes
• Tests
• Documentation

[ajdapretnar]

Counting nans works for discrete but not for string.

[janezd]

Counting nans works for discrete but not for string.

I don't get this one. I removed the column with counts of missing values.

Trying this I discovered and fixed another bug - if categorical variable was a meta, the widget crashed.

[janezd]

I don't get this one. I removed the column with counts of missing values.

Maybe I do - maybe I just fell into the same trap. Have you been testing Split or Text to Columns? I renamed the widget. :)

[erikafuna]

@ajdapretnar and @janezd, we forgot about this one, didn't we?

[codecov-commenter]

Codecov Report

❌ Patch coverage is 93.02326% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 35.99%. Comparing base (5ef0d45) to head (a74ea06).
⚠️ Report is 49 commits behind head on master.

Files with missing lines	Patch %	Lines
...rangecontrib/prototypes/widgets/owtexttocolumns.py	93.02%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #253      +/-   ##
==========================================
+ Coverage   33.92%   35.99%   +2.06%     
==========================================
  Files           9       10       +1     
  Lines        1515     1478      -37     
==========================================
+ Hits          514      532      +18     
+ Misses       1001      946      -55     

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[janezd]

Not at all. I seldom go to sleep without thinking about it, and @ajdapretnar and I discuss it at least once a week, sometimes even daily.

Seriously, how did you stumble upon this? Yes, it could be merged, I think. I also updated it (now that biolab/orange3#6058 is merged and released). @ajdapretnar, check and merge at will. We can also move it from prototypes; as I recall, it is used for some fields from google forms.

[markotoplak]

Failing tests are also not an issue here and we'll fix them later. @erikafuna found a question posted on FB regarding this widget and she asked me which widget that was. Then we searched and found this. Merging. If @ajdapretnar has any comments, let's fix them later.