# Difference between revisions of "ApCoCoA:Num.EigenValuesAndVectors"

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Therefore the input matrix A has to be rectangular! | Therefore the input matrix A has to be rectangular! | ||

It is implemented in the ApCoCoA server, so you need a running server. It was not implemented in version 0.99.4 or previous. Also please keep in mind this method is based on blas/Lapack's eigenvalue solver and uses floating point arithmetic. This is not an exact, algebraic method! | It is implemented in the ApCoCoA server, so you need a running server. It was not implemented in version 0.99.4 or previous. Also please keep in mind this method is based on blas/Lapack's eigenvalue solver and uses floating point arithmetic. This is not an exact, algebraic method! | ||

− | The output contains first of a matrix B, where | + | The output contains first of a matrix B, where each row contains one of A's eigenvalues. The first column contains the eigenvalue's real part, the second the imaginary. |

− | The second | + | The second element of the returned list is a matrix of the size of A, containing the (right hand) eigenvectors of A. |

To compute only the left hand's eigenvectors apply this method to Transposed(A). | To compute only the left hand's eigenvectors apply this method to Transposed(A). | ||

<example> | <example> |

## Revision as of 09:58, 17 September 2008

<command> <title>Numerical.EigenValuesAndVectors</title> <short_description>eigenvalues of a matrix</short_description>

<syntax> $numerical.EigenValuesAndVectors(A:Matrix):List </syntax>

<description>

This function returns a List of two matrices, containing numerical approximation to A's eigenvalues and (right hand) eigenvectors. Therefore the input matrix A has to be rectangular! It is implemented in the ApCoCoA server, so you need a running server. It was not implemented in version 0.99.4 or previous. Also please keep in mind this method is based on blas/Lapack's eigenvalue solver and uses floating point arithmetic. This is not an exact, algebraic method! The output contains first of a matrix B, where each row contains one of A's eigenvalues. The first column contains the eigenvalue's real part, the second the imaginary. The second element of the returned list is a matrix of the size of A, containing the (right hand) eigenvectors of A. To compute only the left hand's eigenvectors apply this method to Transposed(A). <example> A:=Mat([[1,2,7,18],[2,4,9,12],[23,8,9,10],[7,5,3,2]]); Numerical.EigenValuesAndVectors(A); -- CoCoAServer: computing Cpu Time = 0.0038

[Mat([

[2038617447977453/70368744177664, 1593056728295919/4503599627370496, 0, 1717983664400761/562949953421312], [-3850002255576293/281474976710656, 1593056728295919/4503599627370496, 0, -1717983664400761/562949953421312]

]), Mat([

[-7110239176083849/18014398509481984, -5241040126502889/9007199254740992, -569232410323621/18014398509481984, 4695168387448581/18014398509481984], [-7846388397589843/18014398509481984, -3981313256671163/9007199254740992, -2719422585742633/9007199254740992, -4930385173711605/9007199254740992], [-3437594604471165/4503599627370496, 2800381393796867/4503599627370496, 6128985174171139/9007199254740992, 0], [-1207381852306067/4503599627370496, 634514467740541/2251799813685248, -2469130937097749/9007199254740992, 6644460631770309/144115188075855872]

])]

</example>

</description> <seealso> <see>Introduction to CoCoAServer</see> <see>Numerical.QR</see> <see>Numerical.SVD</see> <see>Numerical.EigenValues</see> <see>Numerical.EigenValuesAndAllVectors</see> </seealso> <types> <type>cocoaserver</type> </types> <key>heldt</key> <key>numerical.eigenvaluesandvectors</key> <wiki-category>Package_Numerical</wiki-category> </command>