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CppMatrix.md

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C++) Matrix

matrix is a two-dimensional container (that is a container in which two values are needed to retrieve an element). For one-dimensional containers, go to the container page.

There exists no std::matrix (yet).

Possibilities are:

  1. C++98STL std::vector<std::vector<int> >
  2. C++11STL std::array<std::array<int> >
  3. Boost boost::multi_array
  4. Boost boost::numeric::ublas::matrix
  5. blitz::Array
  6. Techsoft's matrix
  7. Flood::Matrix

These possibilities are described below in more detail.

STL std::vector<std::vector<int> >

A std::vector can contain a collection of std::vectors. If all std::vectors in this collection are of the same size, one has a matrix.

When using std::vector<std::vector<int> > for a two-dimensional matrix, the choice between x-y-ordering or y-x-ordering must be made. The run-time speed difference does not reside in individual element read/write, but when obtaining a row or collumn: in a y-x-ordered std::vector<std::vector<int> > an individual row can be obtained, in an x-y-ordered std::vector<std::vector<int> > an individual collumn can be obtained.

Below is an example of a y-x-ordered std::vector<std::vector<int> >.

#include <cassert>
#include <vector>

int main()
{
  const int n_rows = 5;
  const int n_cols = 10;
  //Create the y-x-ordered 2D-vector
  std::vector<std::vector<int> > v(n_rows, std::vector<int>(n_cols,0),
  const int y = n_rows - 1;
  const int x = n_cols - 1;
  assert(y < static_cast<int>(v.size()),
  assert(x < static_cast<int>(v[y].size()),
  v[y][x] = 10; //y-x-ordered
}
``` 

### [std::vector](CppStdVector.md)&lt;[std::vector](CppStdVector.md)&lt;[int](CppInt.md)&gt; &gt; [code snippets](CppCodeSnippets.md)

Note that some of these [code snippets](CppCodeSnippets.md) also work
on other [containers](CppContainer.md).

1.  [Convert Matrix&lt;X&gt; to Matrix&lt;Y&gt;, ConvertMatrix](CppConvertMatrix.md)
2.  [Convert std::vector&lt;std::vector&lt;X&gt; &gt; to std::vector&lt;std::vector&lt;Y&gt; &gt;, ConvertMatrix](CppConvertMatrix.md)
3.  [Convert two 2D std::vector&lt;X&gt; to 2D std::vector&lt;Y&gt;, ConvertMatrix](CppConvertMatrix.md)
4.  [ConvertMatrix, convert Matrix&lt;X&gt; to Matrix&lt;Y&gt;](CppConvertMatrix.md)
5.  [ConvertMatrix, convert std::vector&lt;std::vector&lt;X&gt; &gt; to std::vector&lt;std::vector&lt;Y&gt; &gt;](CppConvertMatrix.md)
6.  [ConvertMatrix, convert two 2D std::vector&lt;X&gt; to 2D std::vector&lt;Y&gt;](CppConvertMatrix.md)
7.  [Get the maximal element of a 2D container, MaxElement](CppMaxElement.md)
8.  [Get the minimum element of a 2D container, MinElement](CppMinElement.md)
9.  [Get the sizes of the std::vectors in a 2D std::vector, GetSizes](CppGetSizes.md)
10. [Get the sum of a 2D std::vector, GetSum](CppGetSumMatrix.md)
11. [GetSizes, get the sizes of the std::vectors in a 2D std::vector](CppGetSizes.md)
12. [GetSum, get the sum of a 2D std::vector](CppGetSumMatrix.md)
13. [MaxElement, get the maximal element of a 2D container](CppMaxElement.md)
14. [MinElement, get the minimum element of a 2D container](CppMinElement.md)

## ![Boost](PicBoost.png) [boost::multi\_array](CppBoostMulti_array.md)

The [boost::multi\_array](CppBoostMulti_array.md) (part of the
[Boost](CppBoost.md) library) is not only support a two-dimensional
matrix, but to many more dimensions.

When using [C++ Builder](CppBuilder.md) 6.0, this does not
[compile](CppCompiler.md) (it results in the [compile
error](CppCompileError.md) [borland.hpp: Only member functions may be
'const' or
'volatile'](CppCompileErrorBorlandHppOnlyMemberFunctionsMayBeConstOrVolatile.md)).

## ![Boost](PicBoost.png) [boost::numeric::ublas::matrix](CppUblasMatrix.md)

The [boost::numeric::ublas::matrix](CppUblasMatrix.md) (part of the
[Boost.uBLAS](CppUblas.md) [library](CppLibrary.md)) support a
two-dimensional matrix.

See [boost::numeric::ublas::matrix](CppUblasMatrix.md).

-   ![OKAY](PicGreen.png)![Qt Creator](PicQtCreator.png) In [Qt Creator](CppQtCreator.md) [boost::numeric::ublas::matrix](CppUblasMatrix.md) works fine
-   ![FAIL](PicRed.png)![C++ Builder](PicCppBuilder.png) In [C++ Builder](CppBuilder.md) 6.0, this does not [compile](CppCompiler.md) (it results in the [compile error](CppCompileError.md) [Your compiler and/or configuration is unsupported by this verions of uBLAS](CppCompileErrorYourCompilerAndOrConfigurationIsUnsupportedByThisVerionsOfUblas.md))

## blitz::Array

The blitz::Array (part of the [Blitz++](CppBlitzpp.md)
[library](CppLibrary.md)) is not only support a two-dimensional matrix,
but to many more dimensions.

When using [C++ Builder](CppBuilder.md) 6.0, this does not
[compile](CppCompiler.md) (it results in the [compile
error](CppCompileError.md) [bzconfig.h: Unknown
compiler](CppCompileErrorBzconfigHunknownCompiler.md)).

## [Techsoft](http://www.techsoftpl.com/matrix)'s matrix

[Techsoft](http://www.techsoftpl.com/matrix)'s matrix supports a
x-y-ordered two-dimensional matrix.

```c++ 
#include <cassert>
#include <techsoft/matrix.h>

int main()
{
  const int n_rows = 5;
  const int n_cols = 10;
  math::matrix<int> v(n_rows,n_cols,
  const int y = n_rows - 1;
  const int x = n_cols - 1;
  assert(v(x,y)==0,
  v(x,y) = 10;
  assert(v(x,y)==10,
}

Flood::Matrix

The Flood::Matrix (from the Flood library) supports a x-y-ordered two-dimensional matrix.

#include <cassert>
#include <flood/utilities/matrix.h>
 
int main()
{
  const int n_rows = 5;
  const int n_cols = 10;
  Flood::Matrix<int> v(n_rows,n_cols,
  const int y = n_rows - 1;
  const int x = n_cols - 1;
  assert( x < v.getNumberOfRows(),
  assert( y < v.getNumberOfColumns(),
  assert(v[x][y]==0,
  v[x][y] = 10;
  assert(v[x][y]==10,
}

External links

  1. Wikipedia page about matrices
  2. Boost page about boost::multi_array
  3. Blitz++ homepage
  4. Techsoft homepage

References

  1. Wikipedia page about matrices