On 01/28/2013 11:32 AM, Martin Drautzburg wrote:

On Monday, 28. January 2013 19:37:53 Bryce Verdier wrote:

Hi All,

At the moment I have a list of lists. The inner list is a coordinate,
like (x,y) but is [x,y] instead. What I would like to do is group all
the x's into one list, and the y's into another. I know I can do this
with calling 2 maps on the container, but I would also like to do this
in one iteration.

Something like this?
        groupMe  = foldl (\[rx,ry] [x,y] -> [x:rx,y:ry]) [[],[]]


*Main> groupMe [[1,2],[1,3],[2,3]]
[[2,1,1],[3,3,2]]

Thank you all for your responses. This is what I ultimately went with (pasted below). If anyone would like to share a way to improve this (because I know it can be), please share. I'm still learning. :)

module Main where

import qualified Data.Text as T

import qualified Data.Text.IO as TI (readFile)
import Data.List (transpose)
import Numeric.GSL.Fitting.Linear (linear)
import Data.Packed.Vector (fromList)

buildList :: IO [[T.Text]]
buildList = TI.readFile "lin_reg_data.txt" >>= return . transpose . map (T.split (=='_')) . T.lines

main :: IO ()
main = do
    values <- buildList
    let values2 = map (fromList . map (\x -> read (T.unpack x):: Double)) values
    print [linear (head values2) (last values2)]



Warm regards,
Bryce

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