Eigen::Map Class Reference

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Detailed Description

A matrix or vector expression mapping an existing array of data.

Template Parameters:

PlainObjectType	the equivalent matrix type of the mapped data
MapOptions	specifies whether the pointer is Aligned, or Unaligned. The default is Unaligned.
StrideType	optionnally specifies strides. By default, Map assumes the memory layout of an ordinary, contiguous array. This can be overridden by specifying strides. The type passed here must be a specialization of the Stride template, see examples below.

This class represents a matrix or vector expression mapping an existing array of data. It can be used to let Eigen interface without any overhead with non-Eigen data structures, such as plain C arrays or structures from other libraries. By default, it assumes that the data is laid out contiguously in memory. You can however override this by explicitly specifying inner and outer strides.

Here's an example of simply mapping a contiguous array as a column-major matrix:

Output:

If you need to map non-contiguous arrays, you can do so by specifying strides:

Here's an example of mapping an array as a vector, specifying an inner stride, that is, the pointer increment between two consecutive coefficients. Here, we're specifying the inner stride as a compile-time fixed value.

Output:

Here's an example of mapping an array while specifying an outer stride. Here, since we're mapping as a column-major matrix, 'outer stride' means the pointer increment between two consecutive columns. Here, we're specifying the outer stride as a runtime parameter. Note that here OuterStride<> is a short version of OuterStride<Dynamic> because the default template parameter of OuterStride is Dynamic

Output:

For more details and for an example of specifying both an inner and an outer stride, see class Stride.

Tip: to change the array of data mapped by a Map object, you can use the C++ placement new syntax:

Example:

Output:

This class is the return type of Matrix::Map() but can also be used directly.

See also:

Matrix::Map(), TopicStorageOrders

Inheritance diagram for Eigen::Map:

List of all members.

Public Types
typedef MapBase< Map >	Base
typedef Base::PointerType	PointerType
typedef const Scalar *	PointerArgType
Public Member Functions
PointerType	cast_to_pointer_type (PointerArgType ptr)
Index	innerStride () const
Index	outerStride () const
	Map (PointerArgType data, const StrideType &stride=StrideType())
	Constructor in the fixed-size case.
	Map (PointerArgType data, Index size, const StrideType &stride=StrideType())
	Constructor in the dynamic-size vector case.
	Map (PointerArgType data, Index rows, Index cols, const StrideType &stride=StrideType())
	Constructor in the dynamic-size matrix case.
Protected Attributes
StrideType	m_stride

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Member Typedef Documentation

typedef MapBase<Map> Eigen::Map::Base

Definition at line 123 of file Core.

typedef const Scalar* Eigen::Map::PointerArgType

Definition at line 129 of file Core.

typedef Base::PointerType Eigen::Map::PointerType

Definition at line 127 of file Core.

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Constructor & Destructor Documentation

Eigen::Map::Map	(	PointerArgType	data,
		const StrideType &	stride = StrideType()
	)		[inline]

Constructor in the fixed-size case.

Parameters:

data	pointer to the array to map
stride	optional Stride object, passing the strides.

Definition at line 154 of file Core.

Eigen::Map::Map	(	PointerArgType	data,
		Index	size,
		const StrideType &	stride = StrideType()
	)		[inline]

Constructor in the dynamic-size vector case.

Parameters:

data	pointer to the array to map
size	the size of the vector expression
stride	optional Stride object, passing the strides.

Definition at line 166 of file Core.

Eigen::Map::Map	(	PointerArgType	data,
		Index	rows,
		Index	cols,
		const StrideType &	stride = StrideType()
	)		[inline]

Constructor in the dynamic-size matrix case.

Parameters:

data	pointer to the array to map
rows	the number of rows of the matrix expression
cols	the number of columns of the matrix expression
stride	optional Stride object, passing the strides.

Definition at line 179 of file Core.

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Member Function Documentation

PointerType Eigen::Map::cast_to_pointer_type

(

PointerArgType

ptr

)

[inline]

Definition at line 130 of file Core.

Index Eigen::Map::innerStride

(

)

const [inline]

Definition at line 136 of file Core.

Index Eigen::Map::outerStride

(

)

const [inline]

Definition at line 141 of file Core.

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Member Data Documentation

StrideType Eigen::Map::m_stride [protected]

Definition at line 189 of file Core.