Exporting matrix values to a file

In data analysis and machine learning, matrices are a popular data structure that often need to be exported and imported into the program. In this recipe, we will export a sample matrix using the Repa I/O library.

Getting ready

Install the repa-io library using cabal as follows:

$ cabal install repa-io

How to do it…

Create a new file, which we name Main.hs, and insert the code explained in the following steps:

1. Import the relevant libraries as follows:

   import Data.Array.Repa.IO.Matrix
   import Data.Array.Repa

2. Define a 4 x 3 matrix as follows:

   x :: Array U DIM2 Int 
   x = fromListUnboxed (Z :. (4::Int) :. (3::Int)) 
     [ 1, 2, 9, 10
     , 4, 3, 8, 11
     , 5, 6, 7, 12 ]

3. Write the matrix to a file as follows:

   main = writeMatrixToTextFile "output.dat" x

How it works…

The matrix is represented simply as a list of its elements in row-major order. The first two lines of the file define the type of data and the dimensions.

There's more…

To read a matrix...