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Transpositions< SizeAtCompileTime, MaxSizeAtCompileTime, IndexType > Class Template Reference
Core module

Detailed Description

template<int SizeAtCompileTime, int MaxSizeAtCompileTime, typename IndexType>
class Eigen::Transpositions< SizeAtCompileTime, MaxSizeAtCompileTime, IndexType >

Represents a sequence of transpositions (row/column interchange)

Parameters
SizeAtCompileTimethe number of transpositions, or Dynamic
MaxSizeAtCompileTimethe maximum number of transpositions, or Dynamic. This optional parameter defaults to SizeAtCompileTime. Most of the time, you should not have to specify it.

This class represents a permutation transformation as a sequence of n transpositions $[T_{n-1} \ldots T_{i} \ldots T_{0}]$. It is internally stored as a vector of integers indices. Each transposition $ T_{i} $ applied on the left of a matrix ( $ T_{i} M$) interchanges the rows i and indices[i] of the matrix M. A transposition applied on the right (e.g., $ M T_{i}$) yields a column interchange.

Compared to the class PermutationMatrix, such a sequence of transpositions is what is computed during a decomposition with pivoting, and it is faster when applying the permutation in-place.

To apply a sequence of transpositions to a matrix, simply use the operator * as in the following example:

* Transpositions tr;
* MatrixXf mat;
* mat = tr * mat;
*

In this example, we detect that the matrix appears on both side, and so the transpositions are applied in-place without any temporary or extra copy.

See Also
class PermutationMatrix

Inherits TranspositionsBase< Derived >.

Public Member Functions

const Index & coeff (Index i) const
 
Index & coeffRef (Index i)
 
const IndicesType & indices () const
 
IndicesType & indices ()
 
Transpose< TranspositionsBase > inverse () const
 
const Index & operator() (Index i) const
 
Index & operator() (Index i)
 
template<typename OtherDerived >
Transpositions & operator= (const TranspositionsBase< OtherDerived > &other)
 
const Index & operator[] (Index i) const
 
Index & operator[] (Index i)
 
void resize (int newSize)
 
void setIdentity ()
 
Index size () const
 
Transpose< TranspositionsBase > transpose () const
 
template<typename OtherDerived >
 Transpositions (const TranspositionsBase< OtherDerived > &other)
 
template<typename Other >
 Transpositions (const MatrixBase< Other > &a_indices)
 
 Transpositions (Index size)
 

Constructor & Destructor Documentation

Transpositions ( const TranspositionsBase< OtherDerived > &  other)
inline

Copy constructor.

Transpositions ( const MatrixBase< Other > &  a_indices)
inlineexplicit

Generic constructor from expression of the transposition indices.

Transpositions ( Index  size)
inline

Constructs an uninitialized permutation matrix of given size.

Member Function Documentation

const Index& coeff ( Index  i) const
inlineinherited

Direct access to the underlying index vector

Index& coeffRef ( Index  i)
inlineinherited

Direct access to the underlying index vector

const IndicesType& indices ( ) const
inline

const version of indices().

IndicesType& indices ( )
inline
Returns
a reference to the stored array representing the transpositions.
Transpose<TranspositionsBase> inverse ( ) const
inlineinherited
Returns
the inverse transformation
const Index& operator() ( Index  i) const
inlineinherited

Direct access to the underlying index vector

Index& operator() ( Index  i)
inlineinherited

Direct access to the underlying index vector

Transpositions& operator= ( const TranspositionsBase< OtherDerived > &  other)
inline

Copies the other transpositions into *this

const Index& operator[] ( Index  i) const
inlineinherited

Direct access to the underlying index vector

Index& operator[] ( Index  i)
inlineinherited

Direct access to the underlying index vector

void resize ( int  newSize)
inlineinherited

Resizes to given size.

void setIdentity ( )
inlineinherited

Sets *this to represents an identity transformation

Index size ( ) const
inlineinherited
Returns
the number of transpositions
Transpose<TranspositionsBase> transpose ( ) const
inlineinherited
Returns
the tranpose transformation
The documentation for this class was generated from the following file: