Put some space between bars in histogram ac-plot

[houshuang]

[lfaucon]

That's not as easy as it seems.

• On the example you show we have a discreet distribution with values 0, 1, 2 and 3. In that case we should use a bar-plot instead of an histogram.
• Histograms are for continuous distributions so it's important that there is no space between bars otherwise some values will not be shown. It can be good to use an histogram for a discreet distribution when it is numerical and when it has too many possible values to be each shown with one bar (for example size in centimeters).

I suggest to add a visualization option for bar-plot and that the teacher will decide which to use