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Extend tutorial page on broadcasting to reflect recent changes.

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This commit is contained in:
Jitse Niesen 2011-12-01 21:16:07 +00:00
parent b85bcd91bf
commit a0bcaa88af
2 changed files with 21 additions and 6 deletions
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8
Eigen/src/Core/VectorwiseOp.h
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@ -561,7 +561,7 @@ template<typename ExpressionType, int Direction> class VectorwiseOp
* Example: \include MatrixBase_colwise.cpp
* Output: \verbinclude MatrixBase_colwise.out
*
* \sa rowwise(), class VectorwiseOp
* \sa rowwise(), class VectorwiseOp, \ref TutorialReductionsVisitorsBroadcasting
*/
template<typename Derived>
inline const typename DenseBase<Derived>::ConstColwiseReturnType
@ -572,7 +572,7 @@ DenseBase<Derived>::colwise() const
/** \returns a writable VectorwiseOp wrapper of *this providing additional partial reduction operations
*
* \sa rowwise(), class VectorwiseOp
* \sa rowwise(), class VectorwiseOp, \ref TutorialReductionsVisitorsBroadcasting
*/
template<typename Derived>
inline typename DenseBase<Derived>::ColwiseReturnType
@ -586,7 +586,7 @@ DenseBase<Derived>::colwise()
* Example: \include MatrixBase_rowwise.cpp
* Output: \verbinclude MatrixBase_rowwise.out
*
* \sa colwise(), class VectorwiseOp
* \sa colwise(), class VectorwiseOp, \ref TutorialReductionsVisitorsBroadcasting
*/
template<typename Derived>
inline const typename DenseBase<Derived>::ConstRowwiseReturnType
@ -597,7 +597,7 @@ DenseBase<Derived>::rowwise() const
/** \returns a writable VectorwiseOp wrapper of *this providing additional partial reduction operations
*
* \sa colwise(), class VectorwiseOp
* \sa colwise(), class VectorwiseOp, \ref TutorialReductionsVisitorsBroadcasting
*/
template<typename Derived>
inline typename DenseBase<Derived>::RowwiseReturnType

19
doc/C07_TutorialReductionsVisitorsBroadcasting.dox
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@ -191,12 +191,27 @@ This can be accomplished with:
\verbinclude Tutorial_ReductionsVisitorsBroadcasting_broadcast_simple.out
</td></tr></table>
We can interpret the instruction <tt>mat.colwise() += v</tt> in two equivalent ways. It adds the vector \c v
to every column of the matrix. Alternatively, it can be interpreted as repeating the vector \c v four times to
form a four-by-two matrix which is then added to \c mat:
\f[
\begin{bmatrix} 1 & 2 & 6 & 9 \\ 3 & 1 & 7 & 2 \end{bmatrix}
+ \begin{bmatrix} 0 & 0 & 0 & 0 \\ 1 & 1 & 1 & 1 \end{bmatrix}
= \begin{bmatrix} 1 & 2 & 6 & 9 \\ 4 & 2 & 8 & 3 \end{bmatrix}.
\f]
The operators <tt>-=</tt>, <tt>+</tt> and <tt>-</tt> can also be used column-wise and row-wise. On arrays, we
can also use the operators <tt>*=</tt>, <tt>/=</tt>, <tt>*</tt> and <tt>/</tt> to perform coefficient-wise
multiplication and division column-wise or row-wise. These operators are not available on matrices because it
is not clear what they would do. If you want multiply column 0 of a matrix \c mat with \c v(0), column 1 with
\c v(1), and so on, then use <tt>mat = mat * v.asDiagonal()</tt>.
It is important to point out that the vector to be added column-wise or row-wise must be of type Vector,
and cannot be a Matrix. If this is not met then you will get compile-time error. This also means that
broadcasting operations can only be applied with an object of type Vector, when operating with Matrix.
The same applies for the Array class, where the equivalent for VectorXf is ArrayXf.
The same applies for the Array class, where the equivalent for VectorXf is ArrayXf. As always, you should
not mix arrays and matrices in the same expression.
Therefore, to perform the same operation row-wise we can do:
To perform the same operation row-wise we can do:
<table class="example">
<tr><th>Example:</th><th>Output:</th></tr>