purescript-dataframe

A datastructure designed to be used with queries as well as a type for queries. There is also semantics for combining the queries.

main = do
  let df = init [1, 2, 3, 4, 5, 6, 7]
      q = filter (\x -> x > 3) `chain`
          mutate show `chain`
          trim 3
  putStrLn $ runQuery q df

bower install purescript-dataframe

The idea of a Query type is that we want to have a type-safe way to chain operations on dataframes and we want to maintain the original dataset throughout the query. In other data processing languages this is a common source of error, especially when mutating rows.

The set of dataframe operations are based on what's offered by the dplyr R package.

• filter :: forall r. (r -> Boolean) -> Query (DataFrame r) (Dataframe r) filter rows of the DataFrame
• group :: forall r g. Ord g => (r -> g) -> Query (DataFrame r) (DataFrame {group :: g, data :: Dataframe r}) group the rows of the dataframe by some grouping method
• count :: forall r g. Ord g => (r -> g) -> Query (DataFrame r) (DataFrame {group :: g, count :: Int}) group the rows of the dataframe and count the size of the groups
• summarize :: forall r x. (r -> x) -> Query (DataFrame r) (Array x) convert each row of the dataframe to some type and return an array
• mutate :: forall r s. (r -> s) -> Query (DataFrame r) (Dataframe s) change each row of the dataframe to some other type
• sort :: forall r. (r -> r -> Ordering) -> Query (DataFrame r) (Dataframe r) sort the rows of the dataframe given the ordering function
• trim :: forall r. Int -> Query (DataFrame r) (Dataframe r) keep only the first n rows of the DataFrame

The chain :: forall r s t. Query r s -> Query s t -> Query r t function allows us to chain queries and keep the original context.

API documentation is published on Pursuit.

• DataFrames should be able to operate either as a set of columns or a set of rows.
• Queries should do caching