Program g02btfe

!     G02BTF Example Program Text

!     Mark 29.2 Release. NAG Copyright 2023.

!     .. Use Statements ..
      Use nag_library, Only: g02btf, nag_wp, x04ccf
!     .. Implicit None Statement ..
      Implicit None
!     .. Parameters ..
      Real (Kind=nag_wp), Parameter    :: one = 1.0_nag_wp
      Real (Kind=nag_wp), Parameter    :: zero = 0.0_nag_wp
      Integer, Parameter               :: nin = 5, nout = 6
!     .. Local Scalars ..
      Real (Kind=nag_wp)               :: alpha, sw, wt
      Integer                          :: i, ifail, incx, lc, m, n, nprint
      Character (1)                    :: mean
!     .. Local Arrays ..
      Real (Kind=nag_wp), Allocatable  :: c(:), v(:), x(:), xbar(:)
!     .. Intrinsic Procedures ..
      Intrinsic                        :: mod
!     .. Executable Statements ..
      Write (nout,*) 'G02BTF Example Program Results'
      Write (nout,*)

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

!     Read in problem size
      Read (nin,*) mean, m, n, nprint

      lc = (m*m+m)/2
      Allocate (x(m),xbar(m),c(lc),v(lc))

!     Elements of X are stored consecutively
      incx = 1

!     Loop over each observation individually, updating the sums of squares
!     and cross-product matrix at each iteration
      sw = zero
      i = 0
data_lp: Do
        Read (nin,*,Iostat=ifail) wt, x(1:m)
        If (ifail/=0) Then
!         Finished processing all the data
          Exit data_lp
        End If

        i = i + 1

!       Update the sums of squares and cross-products matrix
        ifail = 0
        Call g02btf(mean,m,wt,x,incx,sw,xbar,c,ifail)

!       Display the results, either at the end or every NPRINT iterations
        If (mod(i,nprint)==0 .Or. i==n) Then
          Write (nout,*) '---------------------------------------------'
          Write (nout,99999) 'Observation: ', i, '      Weight = ', wt
          Write (nout,*) '---------------------------------------------'
          Write (nout,*)
          Write (nout,*) 'Means'
          Write (nout,99998) xbar(1:m)
          Write (nout,*)
          Flush (nout)
          ifail = 0
          Call x04ccf('Upper','Non-unit',m,c,                                  &
            'Sums of squares and cross-products',ifail)

!         Convert the sums of squares and cross-products to a variance matrix
          If (sw>one) Then
            alpha = one/(sw-one)
            v(1:lc) = alpha*c(1:lc)
            Write (nout,*)
            Flush (nout)
            ifail = 0
            Call x04ccf('Upper','Non-unit',m,v,'Variance matrix',ifail)
          End If
          Write (nout,*)
        End If
      End Do data_lp

99999 Format (1X,A,I4,A,F13.4)
99998 Format (1X,4F14.4)
    End Program g02btfe