This tile is intended to display a barchart. The expression passed after the with keyword should offer an aggregator. An explicit group by statement is expected.
table T = extend.range(10)
T.X = random.poisson(5 into T)
T.G = "G\{T.N}"
show barchart "My Groups" a1b8 {unit: "$"} with
sum(T.X)
group by T.G