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A 8*8 matrix
with the eigenvalues +/- 10sqrt(10405)
(1020.049...) a double eigenvalue 1000 and
two more eigenvalues near 1019 and 1020,
that is a dense cluster of eigenvalues and in addition
the eigenvalues 0 and 510-100sqrt(26)=0.09805.
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The "bar matrix" (quindiagonal matrix)
with the diagonals 1,..,1; -4,...,-4;
5,6,..,6,5; -4,...,-4; 1,...1,
and the analytically known eigenvalues
16*sin(i*pi/(2(n+1)))**4, i = 1,...,n.
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Generation of a matrix from a given fixed unitary eigensystem
Rij = (sin(ij*pi/(n+1))*sqrt(2/(n+1)), i,j =
1,...,n and freely chooseable eigenvalues.
The entries must be separated by comma or blank
If an eigenvalue Ei occurs m times then you might use the
following shorthand notation:
E1,...,m*Ei,...,En
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Input of a symmetric matrix via its lower triangle:
The data must be given rowwise, each new row beginning on a new line. But a single row may
extend over several lines. Entries to be separated by comma or blank.
A=
The example is for n=3.
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Direct input of a tridiagonal matrix via its diagonal and its first superdiagonal
in turn, hence A(1,1),A(1,2),A(2,2),A(2,3),...,A(n,n)
Entries to be separated by comma or blank. if a value W occurs m times in succession,
you might use the shorthand notation ..,m*W,....
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