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

``` <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>
```