| b |
    b := RTCharterBuilder new.
    b extent: 500 @ 200.
    b points: keys.
    b stackX.
    b allY: [ : each | aBag occurrencesOf: each ].
    b histogramWithBarTitle: #yourself.
    b axisY.
    b newAxisConfiguration plain.
    b axisXTitled: 'MyTitle'.
    b axisX.
    b build.
    ^ b    

using RTGrapher?

Because some methods are missing (#points: #stackX, etc) in the latest version of Roassal2.

Hernán