[ENH] Bar Plot: New widget

[VesnaT]

Issue

Add Bar Plot widget.

Description of changes

I'll add the docs when the UI is approved.

Includes

• Code changes
• Tests
• Documentation

[janezd]

Grouping is more like sorting, isn't it? I think group either have to be clearly separated, or, better still, we could call it sorting and include numeric attributes. In this case I'd even add an option "by value" above "none", and it would be the default.

Annotations will almost never be visible, I suppose. What should we do about them? @irgolic?

[janezd]

What about return escape(str_, entities={"<=": "&#8804;", ">=": "&#8805;", "=\\=": "&#8800;"})?

By the way, for long sequences of replacements I sometimes prefer

reduce(lambda s, t:s.replace(*t), (
    ("<=", "&#8804;"), 
    (">=", "&#8805;"),
    ("<", "&#60;"),
    (">", "&#62;"),
    ("=\\=", "&#8800;")
    )), s)

But this is a matter of taste, and escape fits better here anyway.

[VesnaT]

Same as above..

[VesnaT]

Annotations will almost never be visible, I suppose.

Why?

[janezd]

Annotations will almost never be visible, I suppose.

Why?

I meant, they will almost always overlap.

[VesnaT]

Almost never. They are displayed vertically and one can set the font size.
I added a None option, though.

[janezd]

Even with 100 instances and 10 px labels, this already spreads to > 1000 pixels. But maybe this widget won't be used liked that -- I confess I don't see it's actual use (but it's just me).

Adding None suffices for me. :)

[lanzagar]

Even with 100 instances and 10 px labels, this already spreads to > 1000 pixels. But maybe this widget won't be used liked that -- I confess I don't see it's actual use (but it's just me).

Adding None suffices for me. :)

We were talking about problems when trying to visualize too many bars and how to prevent that. The first idea was to limit it to ~50 rows of data. Then after seeing that the actual bar plot works quite well even for 150 instances, we agreed to limit it to 200 instead. Obviously annotations become a problem in these cases. Since it is now easy to disable them and even to adjust the font sizes I think we can leave the limit at 200, but I would be fine with reducing it to 100 as well.

The main motivation for this widget was to show 3-20 values with a bar chart since that was a common request by people using Orange, who where then forced to use a different tool to produce bar charts of Orange's results. For that scope the annotations should not be a problem and are probably an important feature to have.

[janezd]

Alright then. As I said, I didn't know how this was intended to be used.

[codecov]

Codecov Report

Merging #4923 into master will decrease coverage by 0.04%.
The diff coverage is 79.54%.

@@            Coverage Diff             @@
##           master    #4923      +/-   ##
==========================================
- Coverage   84.66%   84.61%   -0.05%     
==========================================
  Files         284      285       +1     
  Lines       58942    59417     +475     
==========================================
+ Hits        49902    50276     +374     
- Misses       9040     9141     +101