Read a comma-separated value (CSV) bytestream into a series.

Consider the following bytestream read from a file:

latitude,longitude,city
48.856667,2.352222,Paris
40.712778,-74.006111,New York City
25.0375,121.5625,Taipei
-34.603333,-58.381667,Buenos Aires

We want to get a series of the latitude an longitude, indexed by the column "city". First, we need to do is to create a datatype representing the latitude and longitude information, and our index:

data LatLong = MkLatLong { latitude  :: Double
                         , longitude :: Double
                         }
    deriving ( Show )

newtype City = MkCity String
    deriving ( Eq, Ord, Show )

Second, we need to create an instance of FromNamedRecord for our new types:

import Data.Csv ( FromNamedRecord, (.:) )

instance FromNamedRecord LatLong where
    parseNamedRecord r = MkLatLong <$> r .: "latitude"
                                   <*> r .: "longitude"


instance FromNamedRecord City where
    parseNamedRecord r = MkCity <$> r .: "city"

Finally, we're ready to read our stream:

import Data.Series
import Data.Series.IO

main :: IO ()
main = do
    let fp = "pathtomy/file.csv"
    let (latlongs  :: Series City LatLong) = either (error . show) id <$> readCSVFromFile fp
    print latlongs

This is a helper function to read a CSV directly from a filepath. See the documentation for readCSV on how to prepare your types. Then, for example, you can use readCSVFromFile as:

import Data.Series
import Data.Series.IO

main :: IO ()
main = do
    let fp = "pathtomy/file.csv"
    let (latlongs  :: Series City LatLong) = either (error . show) id <$> readCSVFromFile fp
    print latlongs

Read a comma-separated value (CSV) bytestream into a series.

Consider the following bytestream read from a file:

latitude,longitude,city
48.856667,2.352222,Paris
40.712778,-74.006111,New York City
25.0375,121.5625,Taipei
-34.603333,-58.381667,Buenos Aires

We want to get a series of the latitude an longitude, indexed by the column "city". First, we need to do is to create a datatype representing the latitude and longitude information, and our index:

data LatLong = MkLatLong { latitude  :: Double
                         , longitude :: Double
                         }
    deriving ( Show )

newtype City = MkCity String
    deriving ( Eq, Ord, Show )

Second, we need to create an instance of FromNamedRecord for our new types:

import Data.Csv ( FromNamedRecord, (.:) )

instance FromNamedRecord LatLong where
    parseNamedRecord r = MkLatLong <$> r .: "latitude"
                                   <*> r .: "longitude"


instance FromNamedRecord City where
    parseNamedRecord r = MkCity <$> r .: "city"

Finally, we're ready to read our stream:

import Data.Series
import Data.Series.IO

main :: IO ()
main = do
    stream <- (...) -- Read the bytestring from somewhere
    let (latlongs  :: Series City LatLong) = either (error . show) id <$> readCSV stream
    print latlongs

This is a helper function to write a Series directly to CSV. See the documentation for writeCSV on how to prepare your types.