66 lines
1.9 KiB
Plaintext
66 lines
1.9 KiB
Plaintext
namespace Eigen {
|
|
|
|
/** \eigenManualPage TutorialReshapeSlicing Reshape and Slicing
|
|
|
|
%Eigen does not expose convenient methods to take slices or to reshape a matrix yet.
|
|
Nonetheless, such features can easily be emulated using the Map class.
|
|
|
|
\eigenAutoToc
|
|
|
|
\section TutorialReshape Reshape
|
|
|
|
A reshape operation consists in modifying the sizes of a matrix while keeping the same coefficients.
|
|
Instead of modifying the input matrix itself, which is not possible for compile-time sizes, the approach consist in creating a different \em view on the storage using class Map.
|
|
Here is a typical example creating a 1D linear view of a matrix:
|
|
|
|
<table class="example">
|
|
<tr><th>Example:</th><th>Output:</th></tr>
|
|
<tr><td>
|
|
\include Tutorial_ReshapeMat2Vec.cpp
|
|
</td>
|
|
<td>
|
|
\verbinclude Tutorial_ReshapeMat2Vec.out
|
|
</td></tr></table>
|
|
|
|
Remark how the storage order of the input matrix modifies the order of the coefficients in the linear view.
|
|
Here is another example reshaping a 2x6 matrix to a 6x2 one:
|
|
<table class="example">
|
|
<tr><th>Example:</th><th>Output:</th></tr>
|
|
<tr><td>
|
|
\include Tutorial_ReshapeMat2Mat.cpp
|
|
</td>
|
|
<td>
|
|
\verbinclude Tutorial_ReshapeMat2Mat.out
|
|
</td></tr></table>
|
|
|
|
|
|
|
|
\section TutorialSlicing Slicing
|
|
|
|
Slicing consists in taking a set of rows, columns, or elements, uniformly spaced within a matrix.
|
|
Again, the class Map allows to easily mimic this feature.
|
|
|
|
For instance, one can skip every P elements in a vector:
|
|
<table class="example">
|
|
<tr><th>Example:</th><th>Output:</th></tr>
|
|
<tr><td>
|
|
\include Tutorial_SlicingVec.cpp
|
|
</td>
|
|
<td>
|
|
\verbinclude Tutorial_SlicingVec.out
|
|
</td></tr></table>
|
|
|
|
One can olso take one column over three using an adequate outer-stride or inner-stride depending on the actual storage order:
|
|
<table class="example">
|
|
<tr><th>Example:</th><th>Output:</th></tr>
|
|
<tr><td>
|
|
\include Tutorial_SlicingCol.cpp
|
|
</td>
|
|
<td>
|
|
\verbinclude Tutorial_SlicingCol.out
|
|
</td></tr></table>
|
|
|
|
*/
|
|
|
|
}
|