Safe Haskell  None 

Matrix datatype and operations.
Every provided example has been tested.
 data Matrix a
 prettyMatrix :: Show a => Matrix a > String
 nrows :: Matrix a > Int
 ncols :: Matrix a > Int
 forceMatrix :: Matrix a > Matrix a
 matrix :: Int > Int > ((Int, Int) > a) > Matrix a
 fromList :: Int > Int > [a] > Matrix a
 fromLists :: [[a]] > Matrix a
 rowVector :: Vector a > Matrix a
 colVector :: Vector a > Matrix a
 zero :: Num a => Int > Int > Matrix a
 identity :: Num a => Int > Matrix a
 permMatrix :: Num a => Int > Int > Int > Matrix a
 getElem :: Int > Int > Matrix a > a
 (!) :: Matrix a > (Int, Int) > a
 safeGet :: Int > Int > Matrix a > Maybe a
 getRow :: Int > Matrix a > Vector a
 getCol :: Int > Matrix a > Vector a
 getDiag :: Matrix a > Vector a
 setElem :: a > (Int, Int) > Matrix a > Matrix a
 transpose :: Matrix a > Matrix a
 extendTo :: Num a => Int > Int > Matrix a > Matrix a
 mapRow :: (Int > a > a) > Int > Matrix a > Matrix a
 mapCol :: (Int > a > a) > Int > Matrix a > Matrix a
 submatrix :: Int > Int > Int > Int > Matrix a > Matrix a
 minorMatrix :: Int > Int > Matrix a > Matrix a
 splitBlocks :: Int > Int > Matrix a > (Matrix a, Matrix a, Matrix a, Matrix a)
 (<>) :: Matrix a > Matrix a > Matrix a
 (<>) :: Matrix a > Matrix a > Matrix a
 joinBlocks :: (Matrix a, Matrix a, Matrix a, Matrix a) > Matrix a
 multStd :: Num a => Matrix a > Matrix a > Matrix a
 multStrassen :: Num a => Matrix a > Matrix a > Matrix a
 multStrassenMixed :: Num a => Matrix a > Matrix a > Matrix a
 scaleMatrix :: Num a => a > Matrix a > Matrix a
 scaleRow :: Num a => a > Int > Matrix a > Matrix a
 combineRows :: Num a => Int > a > Int > Matrix a > Matrix a
 switchRows :: Int > Int > Matrix a > Matrix a
 luDecomp :: (Ord a, Fractional a) => Matrix a > (Matrix a, Matrix a, Matrix a, a)
 trace :: Num a => Matrix a > a
 diagProd :: Num a => Matrix a > a
 detLaplace :: Num a => Matrix a > a
 detLU :: (Ord a, Fractional a) => Matrix a > a
Matrix type
Type of matrices.
prettyMatrix :: Show a => Matrix a > StringSource
forceMatrix :: Matrix a > Matrix aSource
Builders
O(rows*cols). Generate a matrix from a generator function. Example of usage:
( 1 0 1 2 ) ( 3 2 1 0 ) ( 5 4 3 2 ) matrix 4 4 $ \(i,j) > 2*i  j = ( 7 6 5 4 )
Create a matrix from a nonempty list given the desired size. The list must have at least rows*cols elements. An example:
( 1 2 3 ) ( 4 5 6 ) fromList 3 3 [1..] = ( 7 8 9 )
fromLists :: [[a]] > Matrix aSource
Create a matrix from an nonempty list of nonempty lists. Each list must have the same number of elements. For example:
fromLists [ [1,2,3] ( 1 2 3 ) , [4,5,6] ( 4 5 6 ) , [7,8,9] ] = ( 7 8 9 )
Special matrices
O(rows*cols). The zero matrix of the given size.
zero n m = n 1 ( 0 0 ... 0 0 ) 2 ( 0 0 ... 0 0 ) ( ... ) ( 0 0 ... 0 0 ) n ( 0 0 ... 0 0 )
identity :: Num a => Int > Matrix aSource
O(rows*cols). Identity matrix of the given order.
identity n = n 1 ( 1 0 ... 0 0 ) 2 ( 0 1 ... 0 0 ) ( ... ) ( 0 0 ... 1 0 ) n ( 0 0 ... 0 1 )
:: Num a  
=> Int  Size of the matrix. 
> Int  Permuted row 1. 
> Int  Permuted row 2. 
> Matrix a  Permutation matrix. 
O(rows*cols). Permutation matrix.
permMatrix n i j = i j n 1 ( 1 0 ... 0 ... 0 ... 0 0 ) 2 ( 0 1 ... 0 ... 0 ... 0 0 ) ( ... ... ... ) i ( 0 0 ... 0 ... 1 ... 0 0 ) ( ... ... ... ) j ( 0 0 ... 1 ... 0 ... 0 0 ) ( ... ... ... ) ( 0 0 ... 0 ... 0 ... 1 0 ) n ( 0 0 ... 0 ... 0 ... 0 1 )
When i == j
it reduces to identity
n
.
Accessing
Manipulating matrices
:: a  New value. 
> (Int, Int)  Position to replace. 
> Matrix a  Original matrix. 
> Matrix a  Matrix with the given position replaced with the given value. 
O(1). Replace the value of a cell in a matrix.
transpose :: Matrix a > Matrix aSource
O(rows*cols). The transpose of a matrix. Example:
( 1 2 3 ) ( 1 4 7 ) ( 4 5 6 ) ( 2 5 8 ) transpose ( 7 8 9 ) = ( 3 6 9 )
Extend a matrix to a given size adding zeroes. If the matrix already has the required size, nothing happens. The matrix is never reduced in size. Example:
( 1 2 3 0 0 ) ( 1 2 3 ) ( 4 5 6 0 0 ) ( 4 5 6 ) ( 7 8 9 0 0 ) extendTo 4 5 ( 7 8 9 ) = ( 0 0 0 0 0 )
:: (Int > a > a)  Function takes the current column as additional argument. 
> Int  Row to map. 
> Matrix a  
> Matrix a 
O(rows*cols). Map a function over a row. Example:
( 1 2 3 ) ( 1 2 3 ) ( 4 5 6 ) ( 5 6 7 ) mapRow (\_ x > x + 1) 2 ( 7 8 9 ) = ( 7 8 9 )
:: (Int > a > a)  Function takes the current row as additional argument. 
> Int  Column to map. 
> Matrix a  
> Matrix a 
O(rows*cols). Map a function over a column. Example:
( 1 2 3 ) ( 1 3 3 ) ( 4 5 6 ) ( 4 6 6 ) mapCol (\_ x > x + 1) 2 ( 7 8 9 ) = ( 7 9 9 )
Submatrices
Splitting blocks
:: Int  Starting row 
> Int  Ending row 
> Int  Starting column 
> Int  Ending column 
> Matrix a  
> Matrix a 
O(subrows*subcols). Extract a submatrix given row and column limits. Example:
( 1 2 3 ) ( 4 5 6 ) ( 2 3 ) submatrix 1 2 2 3 ( 7 8 9 ) = ( 5 6 )
:: Int  Row 
> Int  Column 
> Matrix a  Original matrix. 
> Matrix a  Matrix with row 
O(rows*cols). Remove a row and a column from a matrix. Example:
( 1 2 3 ) ( 4 5 6 ) ( 1 3 ) minorMatrix 2 2 ( 7 8 9 ) = ( 7 9 )
:: Int  Row of the splitting element. 
> Int  Column of the splitting element. 
> Matrix a  Matrix to split. 
> (Matrix a, Matrix a, Matrix a, Matrix a)  (TL,TR,BL,BR) 
Make a blockpartition of a matrix using a given element as reference. The element will stay in the bottomright corner of the topleft corner matrix.
( ) (  ) ( ) ( ...  ... ) ( x ) ( x  ) splitBlocks i j ( ) = () , where x = a_{i,j} ( ) (  ) ( ) ( ...  ... ) ( ) (  )
Note that some blocks can end up empty. We use the following notation for these blocks:
( TL  TR ) () ( BL  BR )
Where T = Top, B = Bottom, L = Left, R = Right.
Implementation is done via slicing of vectors.
Joining blocks
(<>) :: Matrix a > Matrix a > Matrix aSource
Horizontally join two matrices. Visually:
( A ) <> ( B ) = ( A  B )
Where both matrices A and B have the same number of rows. This condition is not checked.
(<>) :: Matrix a > Matrix a > Matrix aSource
Vertically join two matrices. Visually:
( A ) ( A ) <> ( B ) = (  ) ( B )
Where both matrices A and B have the same number of columns. This condition is not checked.
joinBlocks :: (Matrix a, Matrix a, Matrix a, Matrix a) > Matrix aSource
Join blocks of the form detailed in splitBlocks
.
Matrix multiplication
About matrix multiplication
Three methods are provided for matrix multiplication.

multStd
: Matrix multiplication following directly the definition. This is the best choice when you know for sure that your matrices are small. 
multStrassen
: Matrix multiplication following the Strassen's algorithm. Complexity grows slower but also some work is added partitioning the matrix. Also, it only works on square matrices of order2^n
, so if this condition is not met, it is zeropadded until this is accomplished. Therefore, its use it is not recommended. 
multStrassenMixed
: This function mixes themultStd
andmultStrassen
methods. It provides a better performance in general. Method(
*
)
of theNum
class uses this function because it gives the best average performance. However, if you know for sure that your matrices are small, you should usemultStd
instead, sincemultStrassenMixed
is going to switch to that function anyway.
Functions
multStd :: Num a => Matrix a > Matrix a > Matrix aSource
Standard matrix multiplication by definition.
multStrassenMixed :: Num a => Matrix a > Matrix a > Matrix aSource
Mixed Strassen's matrix multiplication.
Linear transformations
scaleMatrix :: Num a => a > Matrix a > Matrix aSource
Scale a matrix by a given factor. Example:
( 1 2 3 ) ( 2 4 6 ) ( 4 5 6 ) ( 8 10 12 ) scaleMatrix 2 ( 7 8 9 ) = ( 14 16 18 )
scaleRow :: Num a => a > Int > Matrix a > Matrix aSource
Scale a row by a given factor. Example:
( 1 2 3 ) ( 1 2 3 ) ( 4 5 6 ) ( 8 10 12 ) scaleRow 2 2 ( 7 8 9 ) = ( 7 8 9 )
combineRows :: Num a => Int > a > Int > Matrix a > Matrix aSource
Add to one row a scalar multiple of other row. Example:
( 1 2 3 ) ( 1 2 3 ) ( 4 5 6 ) ( 6 9 12 ) combineRows 2 2 1 ( 7 8 9 ) = ( 7 8 9 )
Switch two rows of a matrix. Example:
( 1 2 3 ) ( 4 5 6 ) ( 4 5 6 ) ( 1 2 3 ) switchRows 1 2 ( 7 8 9 ) = ( 7 8 9 )
Decompositions
luDecomp :: (Ord a, Fractional a) => Matrix a > (Matrix a, Matrix a, Matrix a, a)Source
Matrix LU decomposition with partial pivoting. The result for a matrix M is given in the format (U,L,P,d) where:
 U is an upper triangular matrix.
 L is an unit lower triangular matrix.
 P is a permutation matrix.
 d is the determinant of P.
 PM = LU.
These properties are only guaranteed when the input matrix is invertible. An additional property matches thanks to the strategy followed for pivoting:
 L_(i,j) <= 1, for all i,j.
This follows from the maximal property of the selected pivots, which also leads to a better numerical stability of the algorithm.
Example:
( 1 2 0 ) ( 2 0 2 ) ( 1 0 0 ) ( 0 0 1 ) ( 0 2 1 ) ( 0 2 1 ) ( 1/2 1 0 ) ( 1 0 0 ) luDecomp ( 2 0 2 ) = ( ( 0 0 2 ) , ( 0 1 1 ) , ( 0 1 0 ) , 1 )
Properties
trace :: Num a => Matrix a > aSource
Sum of the elements in the diagonal. See also getDiag
.
Example:
( 1 2 3 ) ( 4 5 6 ) trace ( 7 8 9 ) = 15
diagProd :: Num a => Matrix a > aSource
Product of the elements in the diagonal. See also getDiag
.
Example:
( 1 2 3 ) ( 4 5 6 ) diagProd ( 7 8 9 ) = 45
Determinants
detLaplace :: Num a => Matrix a > aSource
Matrix determinant using Laplace expansion.
If the elements of the Matrix
are instance of Ord
and Fractional
consider to use detLU
in order to obtain better performance.
detLU :: (Ord a, Fractional a) => Matrix a > aSource
Matrix determinant using LU decomposition.