On Wed, Dec 28, 2016 at 9:28 AM, Cody Goodman <codygman.consulting@gmail.com> wrote:

My goal is to take data like this:

                        [ Info 0 "Alcohol" "TX"
                        , Info 1 "Alcohol" "TX"
                        , Info 2 "Pregnancy" "MA"
                        ]

and build a Map like this:

[("MA",[("Pregnancy",1)]),("TX",[("Alcohol",2)])]

You can convert each individual record to a singleton map:

wrapRecord :: Info -> M.Map String (M.Map String Integer)

wrapRecord (Info _ state healthTopic) = M.singleton state (M.singleton healthTopic 1)

and then union all these singletons:

numTopicsPerState = M.unionsWith (M.unionWith (+)) . map wrapRecord $ [Info 0 "Alcohol" "TX", Info 1 "Alcohol" "TX", Info 2 "Pregnancy" "MA"]