NAG Library Manual, Mark 28.4
Interfaces:  FL   CL   CPP   AD
```    Program f07wdfe

!     F07WDF Example Program Text

!     Mark 28.4 Release. NAG Copyright 2022.

!     .. Use Statements ..
Use nag_library, Only: dpftrf, dtfttr, nag_wp, x04caf
!     .. Implicit None Statement ..
Implicit None
!     .. Parameters ..
Integer, Parameter               :: nin = 5, nout = 6
!     .. Local Scalars ..
Integer                          :: i, ifail, info, k, lar1, lda, lenar, &
n, q
Character (1)                    :: transr, uplo
!     .. Local Arrays ..
Real (Kind=nag_wp), Allocatable  :: a(:,:), ar(:)
!     .. Executable Statements ..
Write (nout,*) 'F07WDF Example Program Results'
!     Skip heading in data file
Read (nin,*)
Read (nin,*) n, uplo, transr

lenar = n*(n+1)/2
lda = n
Allocate (ar(lenar),a(lda,n))

!     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
Read (nin,*) ar(i:lenar:lar1)
End Do

!     Factorize A
!     The NAG name equivalent of dpftrf is f07wdf
Call dpftrf(transr,uplo,n,ar,info)

Write (nout,*)
Flush (nout)
If (info==0) Then

!       Convert factor to full array form, and print it
!       The NAG name equivalent of dtfttr is f01vgf
Call dtfttr(transr,uplo,n,ar,a,lda,info)
ifail = 0
Call x04caf(uplo,'Nonunit',n,n,a,lda,'Factor',ifail)

Else
Write (nout,*) 'A is not positive definite'
End If

End Program f07wdfe
```