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NAG Toolbox: nag_matop_dtpttf (f01vj)

Purpose

nag_matop_dtpttf (f01vj) copies a real triangular matrix stored in packed format to Rectangular Full Packed (RFP) format. The RFP storage format is described in Section [Rectangular Full Packed (RFP) Storage] in the F07 Chapter Introduction and the packed storage format is described in Section [Packed storage] in the F07 Chapter Introduction.

Syntax

[arf, info] = f01vj(transr, uplo, n, ap)
[arf, info] = nag_matop_dtpttf(transr, uplo, n, ap)

Description

nag_matop_dtpttf (f01vj) copies a real nn by nn triangular matrix, AA, stored packed format, to RFP format. This function is intended for possible use in conjunction with functions from Chapter F07 where some functions that use triangular matrices store them in RFP format.

References

None.

Parameters

Compulsory Input Parameters

1:     transr – string (length ≥ 1)
Specifies whether the RFP representation of AA is normal or transposed.
transr = 'N'transr='N'
The matrix AA is stored in normal RFP format.
transr = 'T'transr='T'
The matrix AA is stored in transposed RFP format.
Constraint: transr = 'N'transr='N' or 'T''T'.
2:     uplo – string (length ≥ 1)
Specifies whether AA is upper or lower triangular.
uplo = 'U'uplo='U'
AA is upper triangular.
uplo = 'L'uplo='L'
AA is lower triangular.
Constraint: uplo = 'U'uplo='U' or 'L''L'.
3:     n – int64int32nag_int scalar
nn, the order of the matrix AA.
Constraint: n0n0.
4:     ap(n × (n + 1) / 2n×(n+1)/2) – double array
The nn by nn triangular matrix AA, packed by columns.
More precisely,
  • if uplo = 'U'uplo='U', the upper triangle of AA must be stored with element AijAij in ap(i + j(j1) / 2)api+j(j-1)/2 for ijij;
  • if uplo = 'L'uplo='L', the lower triangle of AA must be stored with element AijAij in ap(i + (2nj)(j1) / 2)api+(2n-j)(j-1)/2 for ijij.

Optional Input Parameters

None.

Input Parameters Omitted from the MATLAB Interface

None.

Output Parameters

1:     arf(n × (n + 1) / 2n×(n+1)/2) – double array
The triangular matrix AA in RFP format, as described in Section [Rectangular Full Packed (RFP) Storage] in the F07 Chapter Introduction.
2:     info – int64int32nag_int scalar
info = 0info=0 unless the function detects an error (see Section [Error Indicators and Warnings]).

Error Indicators and Warnings

  info = iinfo=-i
If info = iinfo=-i, parameter ii had an illegal value on entry. The parameters are numbered as follows:
1: transr, 2: uplo, 3: n, 4: ap, 5: arf, 6: info.

Accuracy

Not applicable.

Further Comments

None.

Example

function nag_matop_dtpttf_example
transr = 'n';
uplo   = 'u';
n      = int64(4);
ap = [1.1; 1.2; 2.2; 1.3; 2.3; 3.3; 1.4; 2.4; 3.4; 4.4];
% Print the packed array
fprintf('\n');
[ifail] = ...
    nag_file_print_matrix_real_gen_comp('g', 'x', ap, 'f5.2', 'Packed array ap:', 'i', ...
                {''}, 'n', {''}, int64(80), int64(0));
% Convert to Rectangular Full Packed form
[arf, info] = nag_matop_dtpttf(transr, uplo, n, ap);
% Print the Rectangular Full Packed array
fprintf('\n');
[ifail] = ...
    nag_file_print_matrix_real_gen_comp('g', 'x', arf, 'f5.2', 'RFP packed array arf:', 'i', ...
                {''}, 'n', {''}, int64(80), int64(0))
 

 Packed array ap:
  1  1.10
  2  1.20
  3  2.20
  4  1.30
  5  2.30
  6  3.30
  7  1.40
  8  2.40
  9  3.40
 10  4.40

 RFP packed array arf:
  1  1.30
  2  2.30
  3  3.30
  4  1.10
  5  1.20
  6  1.40
  7  2.40
  8  3.40
  9  4.40
 10  2.20

ifail =

                    0


function f01vj_example
transr = 'n';
uplo   = 'u';
n      = int64(4);
ap = [1.1; 1.2; 2.2; 1.3; 2.3; 3.3; 1.4; 2.4; 3.4; 4.4];
% Print the packed array
fprintf('\n');
[ifail] = x04cb('g', 'x', ap, 'f5.2', 'Packed array ap:', 'i', ...
                {''}, 'n', {''}, int64(80), int64(0));
% Convert to Rectangular Full Packed form
[arf, info] = f01vj(transr, uplo, n, ap);
% Print the Rectangular Full Packed array
fprintf('\n');
[ifail] = x04cb('g', 'x', arf, 'f5.2', 'RFP packed array arf:', 'i', ...
                {''}, 'n', {''}, int64(80), int64(0))
 

 Packed array ap:
  1  1.10
  2  1.20
  3  2.20
  4  1.30
  5  2.30
  6  3.30
  7  1.40
  8  2.40
  9  3.40
 10  4.40

 RFP packed array arf:
  1  1.30
  2  2.30
  3  3.30
  4  1.10
  5  1.20
  6  1.40
  7  2.40
  8  3.40
  9  4.40
 10  2.20

ifail =

                    0



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Chapter Contents
Chapter Introduction
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