NAG Library Manual, Mark 28.6
```    Program f01vgfe

!     F01VGF Example Program Text

!     Mark 28.6 Release. NAG Copyright 2022.

!     .. Use Statements ..
Use nag_library, Only: dtfttr, nag_wp, x04cbf
!     .. Implicit None Statement ..
Implicit None
!     .. Parameters ..
Integer, Parameter               :: inc1 = 1, indent = 0, ncols = 80,    &
nin = 5, nout = 6
Character (1), Parameter         :: diag = 'N', intlabel = 'I',          &
matrix = 'G', nolabel = 'N'
Character (4), Parameter         :: form = 'F5.2'
!     .. Local Scalars ..
Integer                          :: i, ifail, info, k, lar1, lda, lenar, &
n, q
Character (21)                   :: title
Character (1)                    :: transr, uplo
!     .. Local Arrays ..
Real (Kind=nag_wp), Allocatable  :: a(:,:), ar(:)
Character (1)                    :: clabs(1), rlabs(1)
!     .. Executable Statements ..
Write (nout,*) 'F01VGF Example Program Results'
!     Skip heading in data file
Write (nout,*)
Flush (nout)
lda = n
lenar = n*(n+1)/2
Allocate (a(lda,n),ar(lenar))

!     Setup notional dimensions of RFP matrix AR
k = n/2
q = n - k
If (transr=='N' .Or. transr=='n') Then
lar1 = 2*k + 1
Else
lar1 = q
End If

!     Read an RFP matrix into array AR
Do i = 1, lar1
End Do

!     Print the Rectangular Full Packed array
title = 'RFP Packed Array AR:'
ifail = 0
Call x04cbf(matrix,diag,lenar,inc1,ar,lenar,form,title,intlabel,rlabs,   &
nolabel,clabs,ncols,indent,ifail)
Write (nout,*)
Flush (nout)

!     Convert to triangular form
!     The NAG name equivalent of dtfttr is f01vgf
Call dtfttr(transr,uplo,n,ar,a,lda,info)

!     Print the unpacked array
ifail = 0
title = 'Unpacked Matrix A:'
ifail = 0
Call x04cbf(uplo,diag,n,n,a,lda,form,title,intlabel,rlabs,intlabel,      &
clabs,ncols,indent,ifail)

End Program f01vgfe
```