setfillvalue — Set Fill Values

Masks grid data by applying a FillValue to positions matching a reference mask.

Usage

call setfillvalue(mask, idata)
call setfillvalue(mask, idata, num)   ! optional: filter by mask value

Parameter	Type	Description
mask	FPL 2D type	Reference mask (first argument)
idata	FPL type	Data structure to mask — modified in-place (second argument)
num	integer, optional	When present, masks cells where mask%ncdata /= num instead of using FillValue

Behavior

Without num: For every grid cell where mask%ncdata(i,j) == mask%FillValue, the corresponding cells in idata%ncdata are set to idata%FillValue.

With num: For every grid cell where mask%ncdata(i,j) /= num, the data is set to FillValue. Where mask%ncdata(i,j) == num and idata already has FillValue, it is set to 0.

Works with 2D, 3D, and 4D grids of any numeric type.

Code Example

Apply a state-boundary mask to cattle density data:

program main
  use fpl
  implicit none

  type(nc3d_float_llf_ti) :: cattle
  type(nc2d_float_llf)    :: maskara

  character(200) :: ipath_cattle, ipath_mask, opath
  ipath_cattle = "database/cattle_data.nc"
  ipath_mask   = "database/state_mask.nc"
  opath        = "database/cattle_masked.nc"

  ! Read cattle and mask data
  call readgrid(ipath_cattle, cattle)
  call readgrid(ipath_mask, maskara)

  ! Apply FillValue where mask is FillValue
  call setfillvalue(maskara, cattle)

  ! Or filter by a specific mask value (e.g., state code 18):
  ! call setfillvalue(maskara, cattle, 18)

  ! Write masked result
  call writegrid(opath, cattle)

  call dealloc(cattle)
  call dealloc(maskara)
end program main

Compile & Run

gfortran -o setfvalue.out setfvalue.f90 -I/usr/lib64/gfortran/modules/ -lFPL
./setfvalue.out