FIXME: write docs


(mapcat-rows dataset columns f)
Transforms a dataset by performing a mapcat operation on the rows. Each row in the input is transformed to
multiple rows in the output by the given transform function.
dataset: The dataset to transform.
columns: The collection of columns in the output dataset.
f: function (Row -> Seqable Row) which transforms each row in the input into a sequence of new rows in the output. Each output row should contain the
columns passed in the columns parameter.


(melt dataset pivot-keys)
Melt an object into a form suitable for easy casting, like a melt function in R.
It accepts multiple pivot keys (identifier variables that are reproduced for each
row in the output).
(use '(incanter core charts datasets))
(view (with-data (melt (get-dataset :flow-meter) :Subject)
(line-chart :Subject :value :group-by :variable :legend true)))
See for more examples.