db1ink Subroutine

public subroutine db1ink(x, nx, fcn, kx, tx, bcoef, iflag)

Determines the parameters of a function that interpolates the one-dimensional gridded data The interpolating function and its derivatives may subsequently be evaluated by the function db1val.

History

  • Jacob Williams, 10/30/2015 : Created 1D routine.

Arguments

Type IntentOptional Attributes Name
real(kind=wp), intent(in), dimension(nx) :: x

Array of x abcissae. Must be strictly increasing.
integer, intent(in) :: nx

Number of x abcissae
real(kind=wp), intent(in), dimension(nx) :: fcn

Array of function values to interpolate. fcn(i) should contain the function value at the point x(i)
integer, intent(in) :: kx

The order of spline pieces in x (>= 2, < nx). (order = polynomial degree + 1)
real(kind=wp), intent(inout), dimension(nx+kx) :: tx

The knots in the x direction for the spline interpolant. If iflag=0 these are chosen by db1ink. If iflag=1 these are specified by the user. Must be non-decreasing.
real(kind=wp), intent(out), dimension(nx) :: bcoef

Array of coefficients of the b-spline interpolant.
integer, intent(inout) :: iflag

on input: 0 = knot sequence chosen by db1ink. 1 = knot sequence chosen by user. on output: 1 = successful execution. 2 = iflag out of range. 3 = nx out of range. 4 = kx out of range. 5 = x not strictly increasing. 6 = tx not non-decreasing.

Calls

proc~~db1ink~~CallsGraph proc~db1ink db1ink proc~check_inputs check_inputs proc~db1ink->proc~check_inputs proc~dbknot dbknot proc~db1ink->proc~dbknot proc~dbtpcf dbtpcf proc~db1ink->proc~dbtpcf proc~dbintk dbintk proc~dbtpcf->proc~dbintk proc~dbnslv dbnslv proc~dbtpcf->proc~dbnslv proc~dbintk->proc~dbnslv proc~dbnfac dbnfac proc~dbintk->proc~dbnfac proc~dbspvn dbspvn proc~dbintk->proc~dbspvn

Source Code

    subroutine db1ink(x,nx,fcn,kx,tx,bcoef,iflag)

    implicit none

    integer,intent(in)                      :: nx     !! Number of x abcissae
    integer,intent(in)                      :: kx     !! The order of spline pieces in x (>= 2, < nx). (order = polynomial degree + 1)
    real(wp),dimension(nx),intent(in)       :: x      !! Array of x abcissae. Must be strictly increasing.
    real(wp),dimension(nx),intent(in)       :: fcn    !! Array of function values to interpolate. fcn(i) should
                                                      !!    contain the function value at the point x(i)
    real(wp),dimension(nx+kx),intent(inout) :: tx     !! The knots in the x direction for the spline interpolant.
                                                      !!    If iflag=0 these are chosen by [[db1ink]].
                                                      !!    If iflag=1 these are specified by the user.
                                                      !!    Must be non-decreasing.
    real(wp),dimension(nx),intent(out)      :: bcoef  !! Array of coefficients of the b-spline interpolant.
    integer,intent(inout)                   :: iflag  !! **on input:**  0 = knot sequence chosen by [[db1ink]].
                                                      !!                1 = knot sequence chosen by user.
                                                      !! **on output:** 1 = successful execution.
                                                      !!                2 = iflag out of range.
                                                      !!                3 = nx out of range.
                                                      !!                4 = kx out of range.
                                                      !!                5 = x not strictly increasing.
                                                      !!                6 = tx not non-decreasing.


    real(wp),dimension(2*kx*(nx+1)) :: work
    logical :: status_ok

    !check validity of inputs

    call check_inputs('db1ink',&
                        iflag,&
                        nx=nx,&
                        kx=kx,&
                        x=x,&
                        tx=tx,&
                        status_ok=status_ok)

    if (status_ok) then

        !choose knots

        if (iflag == 0) then
            call dbknot(x,nx,kx,tx)
        endif

        !construct b-spline coefficients

        call dbtpcf(x,nx,fcn,nx,1,tx,kx,bcoef,work,iflag)

        if (iflag==0) iflag = 1

    endif

    endsubroutine db1ink