[Haskell-beginners] reorganizing lists

[Sylvain HENRY]

Hi,

What is the point of using Text here?

You may rewrite buildList as follows (using <$> from Control.Applicative):
buildList = transpose . map (T.split (=='_')) . T.lines <$> TI.readFile
"lin_reg_data.txt"

Regards
Sylvain



2013/1/28 Bryce Verdier <bryceverdier at gmail.com>

> 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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