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NAG[f07vuc] NAG[nag_ztbcon] - Estimate condition number of complex band triangular matrix
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Calling Sequence
f07vuc(norm_type, uplo, diag, kd, ab, rcond, 'n'=n, 'fail'=fail)
nag_ztbcon(. . .)
Parameters
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norm_type - String;
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On entry: indicates whether or is estimated.
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is estimated.
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Constraint: , "Nag_OneNorm" or "Nag_InfNorm". .
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uplo - String;
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On entry: indicates whether is upper or lower triangular.
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is upper triangular.
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is lower triangular.
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Constraint: "Nag_Upper" or "Nag_Lower". .
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diag - String;
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On entry: indicates whether is a non-unit or unit triangular matrix.
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is a non-unit triangular matrix.
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Constraint: "Nag_NonUnitDiag" or "Nag_UnitDiag". .
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kd - integer;
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Constraint: . .
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ab - Matrix(1..dim1, 1..dim2, datatype=complex[8], order=order);
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Note: this array may be supplied in Fortran_order or C_order , as specified by order. All array parameters must use a consistent order.
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rcond - assignable;
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Note: On exit the variable rcond will have a value of type float.
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On exit: an estimate of the reciprocal of the condition number of . rcond is set to zero if exact singularity is detected or the estimate underflows. If rcond is less than machine precision, is singular to working precision.
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'n'=n - integer; (optional)
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Default value: the second dimension of the array ab.
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On entry: , the order of the matrix .
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Constraint: . .
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'fail'=fail - table; (optional)
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The NAG error argument, see the documentation for NagError.
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Description
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Purpose
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nag_ztbcon (f07vuc) estimates the condition number of a complex triangular band matrix.
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Error Indicators and Warnings
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"NE_ALLOC_FAIL"
Dynamic memory allocation failed.
"NE_BAD_PARAM"
On entry, argument had an illegal value.
"NE_INT"
On entry, . Constraint: .
On entry, . Constraint: .
"NE_INTERNAL_ERROR"
An internal error has occurred in this function. Check the function call and any array sizes. If the call is correct then please consult NAG for assistance.
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Accuracy
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The computed estimate rcond is never less than the true value , and in practice is nearly always less than , although examples can be constructed where rcond is much larger.
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Examples
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>
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norm_type := "Nag_OneNorm":
uplo := "Nag_Lower":
diag := "Nag_NonUnitDiag":
n := 4:
kd := 2:
ab := Matrix([[0 +0*I , 0 +0*I , -1.94 +4.43*I ], [0 +0*I , -3.39 +3.44*I , 4.12 -4.27*I ], [1.62 +3.68*I , -1.84 +5.53*I , 0.43 -2.66*I ], [-2.77 -1.93*I , 1.74 -0.04*I , 0.44 +0.1*I ]], datatype=complex[8], order='C_order'):
NAG:-f07vuc(norm_type, uplo, diag, kd, ab, rcond, 'n' = n):
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