rgrd2u – regridpack

private subroutine rgrd2u(nx, ny, p, mx, my, q, intpol, w, lw, iw, liw, ier)

subroutine rgrd2u interpolates the nx by ny array p onto the mx by my array q. linear or cubic interpolation is used in each direction (see argument intpol). it is assumed that p and q are values on uniform nx by ny and mx by my grids superimposed on the same rectangle (INCLUDING BOUNDARIES). if p and q are values on nonuniform orthogonal grids and/or if the grid on which q is defined lies within the p grid then subroutine rgrd2 should be used.

method

linear or cubic interpolation (see intpol) is used in each direction for which the q grid is not a subgrid of the p grid. [the mx (my) uniform grid is a subgrid of the nx (ny) uniform grid if and only if mx-1 (my-1) divides nx-1 (ny-1)]. values are set directly without (the need for) interpolation in subgrid directions.

Arguments

Type	Intent		Name
integer,	intent(in)	::	nx	the integer first dimension of p. nx > 1 if intpol(1) = 1 or nx > 3 if intpol(1) = 3 is required (see ier = 2).
integer,	intent(in)	::	ny	the integer second dimension of p. ny > 1 if intpol(2) = 1 or ny > 3 if intpol(2) = 3 is required (see ier = 2).
real(kind=wp),	intent(in)	::	p(nx,ny)	a real(wp) nx by ny array of given values
integer,	intent(in)	::	mx	the integer first dimension of q. mx > 1 is required (see ier = 1)
integer,	intent(in)	::	my	the integer second dimension of q. my > 1 is required (see ier = 1)
real(kind=wp),	intent(out)	::	q(mx,my)	a real(wp) mx by my array of values which are interpolated from p.
integer,	intent(in)	::	intpol(2)	an integer vector of dimension 2 which sets linear or cubic interpolation in each of the x,y directions as follows: intpol(1) = 1 sets linear interpolation in the x direction intpol(1) = 3 sets cubic interpolation in the x direction. intpol(2) = 1 sets linear interpolation in the y direction intpol(2) = 3 sets cubic interpolation in the y direction. values other than 1 or 3 in intpol are not allowed (ier = 3).
real(kind=wp),	intent(inout)	::	w(lw)	a real(wp) work space of length at least lw which must be provided in the routine calling rgrd2u
integer,	intent(in)	::	lw	the integer length of the work space w. let lwx = 1 if mx-1 divides nx-1; otherwise let lwx = mx if intpol(1) = 1 or let lwx = 4*mx if intpol(1) = 3 let lwy = 0 if my-1 divides ny-1; otherwise let lwy = 2mx+my if intpol(2) = 1 or let lwy = 4(mx+my) if intpol(2) = 3 then lw must be greater than or equal to lwx+lwy
integer,	intent(inout)	::	iw(liw)	an integer work space of length at least liw which must be provided in the routine calling rgrd2u
integer,	intent(in)	::	liw	the integer length of the integer work space iw. liw must be greater than or equal to mx+my.
integer,	intent(out)	::	ier	an integer error flag set as follows: ier = 0 if no errors in input arguments are detected ier = 1 if min(mx,my) < 2 ier = 2 if nx < 2 when intpol(1)=1 or nx < 4 when intpol(1)=3 (or) ny < 2 when intpol(2)=1 or ny < 4 when intpol(2)=3. ier = 3 if intpol(1) or intpol(2) is not equal to 1 or 3 ier = 4 if lw or liw is to small (insufficient work space)

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