NAG Library Manual, Mark 29.2
Interfaces:  FL   CL   CPP   AD
```    Program g01apfe

!     G01APF Example Program Text
!     Mark 29.2 Release. NAG Copyright 2023.

!     .. Use Statements ..
Use nag_library, Only: g01apf, nag_wp
!     .. Implicit None Statement ..
Implicit None
!     .. Parameters ..
Integer, Parameter               :: nin = 5, nout = 6
!     .. Local Scalars ..
Real (Kind=nag_wp)               :: eps
Integer                          :: i, ifail, ind, licomm, lrcomm,       &
ltcomm, n, nb, np, nq
Logical                          :: repeat
!     .. Local Arrays ..
Real (Kind=nag_wp), Allocatable  :: q(:), qv(:), rcomm(:), rv(:),        &
trcomm(:)
Integer, Allocatable             :: icomm(:), ticomm(:)
!     .. Executable Statements ..
Write (nout,*) 'G01APF Example Program Results'
Write (nout,*)

!     Skip heading in data file
Read (nin,*)

!     Read in approximation factor
Read (nin,*) eps

!     Read in number of elements in the output vector qv
Read (nin,*) nq
Allocate (qv(nq),q(nq))

!     Read in vector q
Read (nin,*) q(1:nq)

lrcomm = 100
licomm = 400
nb = 20
Allocate (rcomm(lrcomm),icomm(licomm),rv(nb))

ind = 0
repeat = .True.
n = 0

m_lp: Do While (repeat)

If (ind==0 .Or. ind==1) Then
d_lp:     Do i = 1, nb
Read (nin,*,Iostat=ifail) rv(i)
If (ifail/=0) Then
Exit d_lp
End If
End Do d_lp

If (i==1) Then
Exit m_lp
Else If (i-1<nb) Then
nb = i - 1
repeat = .False.
End If
n = n + nb
End If

!       Call the routine
ifail = 1
Call g01apf(ind,rv,nb,eps,np,q,qv,nq,rcomm,lrcomm,icomm,licomm,ifail)
If (ifail/=0) Then
!         This routine is most likely to be used to process large datasets,
!         certain parameter checks will only be done once all the data has
!         been processed. Calling the routine with a hard failure (IFAIL=0)
!         would cause any processing to be lost as the program terminates.
!         It is likely that a soft failure would be more appropriate. This
!         would allow any issues with the input parameters to be resolved
!         without losing any processing already carried out.

!         In this small example we are just calling the routine again with
!         a hard failure so that the error messages are displayed.
ifail = 0
Call g01apf(ind,rv,nb,eps,np,q,qv,nq,rcomm,lrcomm,icomm,licomm,      &
ifail)
End If

!       If ind=2, the communication arrays are too small.
!       Allocate more memory, copy the content back to the communication
!       arrays and call the routine again with the same rv
If (ind==2) Then
If (lrcomm<icomm(1)) Then
ltcomm = lrcomm
lrcomm = icomm(1)
Allocate (trcomm(ltcomm))
trcomm(1:ltcomm) = rcomm(1:ltcomm)
Deallocate (rcomm)
Allocate (rcomm(lrcomm))
rcomm(1:ltcomm) = trcomm(1:ltcomm)
Deallocate (trcomm)
End If
If (licomm<icomm(2)) Then
ltcomm = licomm
licomm = icomm(2)
Allocate (ticomm(ltcomm))
ticomm(1:ltcomm) = icomm(1:ltcomm)
Deallocate (icomm)
Allocate (icomm(licomm))
icomm(1:ltcomm) = ticomm(1:ltcomm)
Deallocate (ticomm)
End If
End If
End Do m_lp

!     Call NAG again with ind=3 to calculate quantiles specified in vector q
ind = 3
ifail = 0
Call g01apf(ind,rv,nb,eps,np,q,qv,nq,rcomm,lrcomm,icomm,licomm,ifail)

!     Print the results
Write (nout,*) 'Input data:'
Write (nout,99999) n, ' observations'
Write (nout,99998) 'eps = ', eps
Write (nout,*)
Write (nout,*) 'Quantile     Result'
Write (nout,99997)(q(i),qv(i),i=1,nq)

99999 Format (1X,I2,A)
99998 Format (1X,A,F5.2)
99997 Format (1X,F7.2,4X,F7.2)
End Program g01apfe
```