[ENH] Discretize: Manual cut points entry

[ales-erjavec]

Issue

Ref: #4914 (comment) (1)

Description of changes

Provide custom values input in Discretize widget.

Includes

• Code changes
• Tests
• Documentation

[codecov]

Codecov Report

Merging #4929 into master will increase coverage by 0.23%.
The diff coverage is 95.63%.

@@            Coverage Diff             @@
##           master    #4929      +/-   ##
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+ Coverage   84.24%   84.48%   +0.23%     
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  Files         283      283              
  Lines       57873    58230     +357     
==========================================
+ Hits        48757    49193     +436     
+ Misses       9116     9037      -79     

[ajdapretnar]

I really like this, but I noticed a couple of things.

1. Manual entry works beautifully, but it would probably be nice to have a tooltip? Something like: "Separate cut-offs with a comma, use point decimal separator." Or perhaps simply: "i.e. 0.5, 1.5, 2.5". 🤷

2. For some reason, I cannot see the tooltip on CC. Even reading it, I am not sure what it does... 🤔 I assumed it copies manual cut-offs from single variable field to the Manual field at the top. If so, it doesn't work for me.

3. Perhaps not a part of this PR, but I have set two cut-offs, i.e. 1.5 and 2.5. There are no values that fall between 1.5 and 2.5. I then try to find them and merge with Edit Domain (merge values option), but nothing happens. Probably there's a bug somewhere. @PrimozGodec

[ales-erjavec]

For some reason, I cannot see the tooltip on CC

Fixed

I assumed it copies manual cut-offs from single variable field to the Manual field at the top. If so, it doesn't work for me.

It copies the current (non-manual) cut points to the edit field and at the same time activates the Manual option.

[janezd]

Nice.

How difficult would it be to somehow indicate an invalid input? I keep forgetting commas. It would be nice to also indicate that the order is not increasing.

Are commas really necessary? Why not also accepting "1 2 3"?

In case of invalid input (e.g. in default), the output is "single_value". Any chance of renaming this to "invalid_cut_of_points"?

In Iris, I set Entropy-MDL as default, then choose sepal width and click CC. I get "2.95, 3.3499999999999996". It would be nicer to have "2.95, 3.35", which are also the values shown in the list view on the left.

Also, when I click Cc, the line edit does not refresh, but this is probably the problem with my Qt -- it does repaint if I hide and show the widget.