Difference between revisions of "ApCoCoA-1:Num.EigenValuesAndVectors"

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(added to category Package_Numerical)
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   <command>
+
   {{Version|1}}
     <title>Numerical.EigenValuesAndVectors</title>
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<command>
     <short_description>Eigenvalues of a matrix</short_description>
+
     <title>Num.EigenValuesAndVectors</title>
 +
     <short_description>Computes the eigenvalues and eigenvectors of a matrix.</short_description>
 
<syntax>
 
<syntax>
$numerical.EigenValuesAndVectors(A:Matrix):List
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Num.EigenValuesAndVectors(A:MAT):[B:MAT, C:MAT, D:Matrix]
 
</syntax>
 
</syntax>
 
     <description>
 
     <description>
This function returns a List of two matrices, containing numerical approximation to A's eigenvalues and (right hand) eigenvectors.  
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<em>Please note:</em> The function(s) explained on this page is/are using the <em>ApCoCoAServer</em>. You will have to start the ApCoCoAServer in order to use it/them.
Therefore the input matrix A has to be rectangular!
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<par/>
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!
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This function returns a list of three matrices containing the numerical approximations of the complex eigenvalues and right eigenvectors of <tt>A</tt>.  
The output contains first of a matrix B, where the number of rows contains one of A's eigenvalues. The first column contains the eigenvalue's real part, the second the imaginary.
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The second part of the list is a matrix of the size of A, containing A's (right hand) eigenvectors.  
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<itemize>
To compute only the left hand's eigenvectors apply this method to Transposed(A).
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<item>@param <em>A</em> A quadratic matrix with rational entries.</item>
 +
<item>@return The output is a list of three matrices <tt>[B:Matrix, C:Matrix, D:Matrix]</tt>. The first matrix <tt>B</tt> contains the complex eigenvalues of the matrix <tt>A</tt>, i.e. the first entry of a column is the real part and the second entry of the same column is the imaginary part of the eigenvalue. The matrices <tt>C</tt> and <tt>D</tt> represent the right eigenvectors of <tt>A</tt>, i.e. the <tt>j</tt>-th column of <tt>C</tt> contains the real part of the right eigenvector corresponding to eigenvalue <tt>j</tt> and the <tt>j</tt>-th column of <tt>D</tt> contains the imaginary part of the same right eigenvector corresponding to eigenvalue <tt>j</tt>.</item>
 +
</itemize>
 +
 
 +
In order to compute the left hand eigenvectors of <tt>A</tt>, apply this command to the transposed matrix of <tt>A</tt> (see <ref>ApCoCoA-1:Transposed|Transposed</ref>).
 +
 
 
<example>
 
<example>
 
A:=Mat([[1,2,7,18],[2,4,9,12],[23,8,9,10],[7,5,3,2]]);  
 
A:=Mat([[1,2,7,18],[2,4,9,12],[23,8,9,10],[7,5,3,2]]);  
Numerical.EigenValuesAndVectors(A);  
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Dec(Num.EigenValuesAndVectors(A),3);  
-- CoCoAServer: computing Cpu Time = 0.0038
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 +
-- CoCoAServer: computing Cpu Time = 0.016
 
-------------------------------
 
-------------------------------
 
[Mat([
 
[Mat([
   [2038617447977453/70368744177664, 1593056728295919/4503599627370496, 0, 1717983664400761/562949953421312],
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   ["28.970", "-13.677", "0.353", "0.353"],
   [-3850002255576293/281474976710656, 1593056728295919/4503599627370496, 0, -1717983664400761/562949953421312]
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   ["0", "0", "3.051", "-3.051"]
 
]), Mat([
 
]), Mat([
   [-7110239176083849/18014398509481984, -5241040126502889/9007199254740992, -569232410323621/18014398509481984, 4695168387448581/18014398509481984],
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   ["0.394", "-0.581", "0.260", "0.260"],
   [-7846388397589843/18014398509481984, -3981313256671163/9007199254740992, -2719422585742633/9007199254740992, -4930385173711605/9007199254740992],
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   ["0.435", "-0.442", "-0.547", "-0.547"],
   [-3437594604471165/4503599627370496, 2800381393796867/4503599627370496, 6128985174171139/9007199254740992, 0],
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  ["0.763", "0.621", "0", "0"],
   [-1207381852306067/4503599627370496, 634514467740541/2251799813685248, -2469130937097749/9007199254740992, 6644460631770309/144115188075855872]
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  ["0.268", "0.281", "0.046", "0.046"]
 +
]), Mat([
 +
  ["0", "0", "-0.031", "0.031"],
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   ["0", "0", "-0.301", "0.301"],
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  ["0", "0", "0.680", "-0.680"],
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   ["0", "0", "-0.274", "0.274"]
 
])]
 
])]
-------------------------------
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--------------------------------------------------------------
 
</example>
 
</example>
 
     </description>
 
     </description>
 
     <seealso>
 
     <seealso>
       <see>Introduction to CoCoAServer</see>
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       <see>ApCoCoA-1:Introduction to CoCoAServer|Introduction to CoCoAServer</see>
       <see>Numerical.QR</see>
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       <see>ApCoCoA-1:Num.QR|Num.QR</see>
       <see>Numerical.SVD</see>
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       <see>ApCoCoA-1:Num.SVD|Num.SVD</see>
       <see>Numerical.EigenValues</see>
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       <see>ApCoCoA-1:Num.EigenValues|Num.EigenValues</see>
       <see>Numerical.EigenValuesAndAllVectors</see>
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       <see>ApCoCoA-1:Num.EigenValuesAndAllVectors|Num.EigenValuesAndAllVectors</see>
 
     </seealso>
 
     </seealso>
     <wiki-category>Package_Numerical</wiki-category>
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    <types>
 +
      <type>apcocoaserver</type>
 +
      <type>matrix</type>
 +
    </types>
 +
    <key>Num.EigenValuesAndVectors</key>
 +
    <key>EigenValuesAndVectors</key>
 +
    <key>numerical.eigenvaluesandvectors</key>
 +
     <wiki-category>ApCoCoA-1:Package_numerical</wiki-category>
 
   </command>
 
   </command>

Latest revision as of 13:47, 29 October 2020

This article is about a function from ApCoCoA-1.

Num.EigenValuesAndVectors

Computes the eigenvalues and eigenvectors of a matrix.

Syntax

Num.EigenValuesAndVectors(A:MAT):[B:MAT, C:MAT, D:Matrix]

Description

Please note: The function(s) explained on this page is/are using the ApCoCoAServer. You will have to start the ApCoCoAServer in order to use it/them.

This function returns a list of three matrices containing the numerical approximations of the complex eigenvalues and right eigenvectors of A.

  • @param A A quadratic matrix with rational entries.

  • @return The output is a list of three matrices [B:Matrix, C:Matrix, D:Matrix]. The first matrix B contains the complex eigenvalues of the matrix A, i.e. the first entry of a column is the real part and the second entry of the same column is the imaginary part of the eigenvalue. The matrices C and D represent the right eigenvectors of A, i.e. the j-th column of C contains the real part of the right eigenvector corresponding to eigenvalue j and the j-th column of D contains the imaginary part of the same right eigenvector corresponding to eigenvalue j.

In order to compute the left hand eigenvectors of A, apply this command to the transposed matrix of A (see Transposed).

Example

A:=Mat([[1,2,7,18],[2,4,9,12],[23,8,9,10],[7,5,3,2]]); 
Dec(Num.EigenValuesAndVectors(A),3); 

-- CoCoAServer: computing Cpu Time = 0.016
-------------------------------
[Mat([
  ["28.970", "-13.677", "0.353", "0.353"],
  ["0", "0", "3.051", "-3.051"]
]), Mat([
  ["0.394", "-0.581", "0.260", "0.260"],
  ["0.435", "-0.442", "-0.547", "-0.547"],
  ["0.763", "0.621", "0", "0"],
  ["0.268", "0.281", "0.046", "0.046"]
]), Mat([
  ["0", "0", "-0.031", "0.031"],
  ["0", "0", "-0.301", "0.301"],
  ["0", "0", "0.680", "-0.680"],
  ["0", "0", "-0.274", "0.274"]
])]
--------------------------------------------------------------

See also

Introduction to CoCoAServer

Num.QR

Num.SVD

Num.EigenValues

Num.EigenValuesAndAllVectors