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index2grid external function
All,
Here is an external function (attached) I wrote to deal with an unusual
gridded data format. Using Ferret lingo you could describe the data as
having the X and Y axes are unraveled and packed, i.e. all X and Y data
points are stored on a single axis with any missing values removed.
My goal was to recreate a usable gridded dataset from this data. Here
is an example of how to use the external function:
use
"http://ferret.pmel.noaa.gov/cgi-bin/dods/nph-dods/data/FreeForm/GLERL/gridded_fields/map_files/erie5km.map.dat";
use
"http://ferret.pmel.noaa.gov/cgi-bin/dods/nph-dods/data/FreeForm/GLERL/gridded_fields/FCAST/no_header.dat";
define axis/x=1:24:1 x24
define axis/y=1:80:1 y80
define grid/y=y80/x=x24 g_80y24x
let d = i[gx=g_80y24x] + j[gy=g_80y24x]
let dep_field = index_to_grid(ii[d=1],jj[d=1],dep[d=1],d)
let lat_field = index_to_grid(ii[d=1],jj[d=1],lat[d=1],d)
let lon_field = index_to_grid(ii[d=1],jj[d=1],lon[d=1],d)
let spd_field = index_to_grid(ii[d=1],jj[d=1],spd[i=2:1016,d=2],d)
let dir_field = index_to_grid(ii[d=1],jj[d=1],dir[i=2:1016,d=2],d)
-- Jonathan Callahan
*
* index_to_grid.F
*
* Jonathan Callahan
* Feb 25th 2002
*
* This function reads in tuples (i,j,val) which correspond
* to the FORTRAN indices of the value. Some sites use this
* method to compress data for gridded fields.
*
* The fourth argument contains the destination grid.
*
* The tuples are assumed to already be defined on an abstract
* X and real Z and T axes. The examples I have seen so far
* are model output at a single level and multiple timesteps.
* The tuple output only corresponds to the X and Y axes and
* is used instead of assigning bad flags or masks.
*
* Note that the FORTRAN indices I and J DO NOT correspond
* to the Ferret indices I and J. The following interpretation
* is made:
*
* FORTRAN I = row number = FERRET J = latitude (perhaps oriented N->S)
* FORTRAN J = col number = FERRET I = longitude
*
* In this subroutine we provide information about
* the function. The user configurable information
* consists of the following:
*
* descr Text description of the function
*
* num_args Required number of arguments
*
* axis_inheritance Type of axis for the result
* ( CUSTOM, IMPLIED_BY_ARGS, NORMAL, ABSTRACT )
* CUSTOM - user defined axis
* IMPLIED_BY_ARGS - same axis as the incoming argument
* NORMAL - the result is normal to this axis
* ABSTRACT - an axis which only has index values
*
* piecemeal_ok For memory optimization:
* axes where calculation may be performed piecemeal
* ( YES, NO )
*
*
* For each argument we provide the following information:
*
* name Text name for an argument
*
* unit Text units for an argument
*
* desc Text description of an argument
*
* axis_influence Are this argument's axes the same as the result grid?
* ( YES, NO )
*
* axis_extend How much does Ferret need to extend arg limits relative to result
*
SUBROUTINE index_to_grid_init(id)
INCLUDE 'ferret_cmn/EF_Util.cmn'
INTEGER id, arg
CALL ef_version_test(ef_version)
* **********************************************************************
* USER CONFIGURABLE PORTION |
* |
* V
CALL ef_set_desc(id,
. 'puts (I,J,VAL) tuples on grid of D' )
CALL ef_set_num_args(id, 4)
CALL ef_set_axis_inheritance(id, IMPLIED_BY_ARGS,
. IMPLIED_BY_ARGS, IMPLIED_BY_ARGS, IMPLIED_BY_ARGS)
CALL ef_set_piecemeal_ok(id, NO, NO, NO, NO)
arg = 1
CALL ef_set_arg_name(id, arg, 'I')
CALL ef_set_arg_desc(id, arg, 'Fortran I index (row) of VAL ')
CALL ef_set_axis_influence(id, arg, NO, NO, NO, NO)
arg = 2
CALL ef_set_arg_name(id, arg, 'J')
CALL ef_set_arg_desc(id, arg, 'Fortran J index (column) of VAL')
CALL ef_set_axis_influence(id, arg, NO, NO, NO, NO)
arg = 3
CALL ef_set_arg_name(id, arg, 'VAL')
CALL ef_set_arg_desc(id, arg, 'Value at grid cell [I,J]')
CALL ef_set_axis_influence(id, arg, NO, NO, YES, YES)
arg = 4
CALL ef_set_arg_name(id, arg, 'D')
CALL ef_set_arg_desc(id, arg, 'destination grid taken from D')
CALL ef_set_axis_influence(id, arg, YES, YES, NO, NO)
* ^
* |
* USER CONFIGURABLE PORTION |
* **********************************************************************
RETURN
END
*
* In this subroutine we compute the result
*
SUBROUTINE index_to_grid_compute(id, arg_1, arg_2, arg_3, arg_4,
. result)
INCLUDE 'ferret_cmn/EF_Util.cmn'
INCLUDE 'ferret_cmn/EF_mem_subsc.cmn'
INTEGER id
REAL bad_flag(1:EF_MAX_ARGS), bad_flag_result
REAL arg_1(mem1lox:mem1hix, mem1loy:mem1hiy,
. mem1loz:mem1hiz, mem1lot:mem1hit)
REAL arg_2(mem2lox:mem2hix, mem2loy:mem2hiy,
. mem2loz:mem2hiz, mem2lot:mem2hit)
REAL arg_3(mem3lox:mem3hix, mem3loy:mem3hiy,
. mem3loz:mem3hiz, mem3lot:mem3hit)
REAL arg_4(mem4lox:mem4hix, mem4loy:mem4hiy,
. mem4loz:mem4hiz, mem4lot:mem4hit)
REAL result(memreslox:memreshix, memresloy:memreshiy,
. memresloz:memreshiz, memreslot:memreshit)
* After initialization, the 'res_' arrays contain indexing information
* for the result axes. The 'arg_' arrays will contain the indexing
* information for each variable's axes.
INTEGER res_lo_ss(4), res_hi_ss(4), res_incr(4)
INTEGER arg_lo_ss(4,1:EF_MAX_ARGS), arg_hi_ss(4,1:EF_MAX_ARGS),
. arg_incr(4,1:EF_MAX_ARGS)
* **********************************************************************
* USER CONFIGURABLE PORTION |
* |
* V
INTEGER i,j,k,l
INTEGER i3,j3,k3,l3
INTEGER index_i,index_j
CALL ef_get_res_subscripts(id, res_lo_ss, res_hi_ss, res_incr)
CALL ef_get_arg_subscripts(id, arg_lo_ss, arg_hi_ss, arg_incr)
CALL ef_get_bad_flags(id, bad_flag, bad_flag_result)
* First -- populate the result with bad flags.
DO 400 i=res_lo_ss(X_AXIS), res_hi_ss(X_AXIS)
DO 300 j=res_lo_ss(Y_AXIS), res_hi_ss(Y_AXIS)
DO 200 k=res_lo_ss(Z_AXIS), res_hi_ss(Z_AXIS)
DO 100 l=res_lo_ss(T_AXIS), res_hi_ss(T_AXIS)
result(i,j,k,l) = bad_flag_result
100 CONTINUE
200 CONTINUE
300 CONTINUE
400 CONTINUE
* Second -- Loop over the K and L axes.
* Put the values where they belong.
*
* Assumption: I,J,VAL are on the same grid.
* Assumption: I is the row # and is associated with a latitude
* Assumption: J is the col # and is associated with a longitude
i = res_lo_ss(X_AXIS)
j = res_lo_ss(Y_AXIS)
k = res_lo_ss(Z_AXIS)
l = res_lo_ss(T_AXIS)
* Note: there should not be a Y axis on argument 3
j3 = arg_lo_ss(Y_AXIS,ARG3)
l3 = arg_lo_ss(T_AXIS,ARG3)
DO 700 l=res_lo_ss(T_AXIS), res_hi_ss(T_AXIS)
k3 = arg_lo_ss(Z_AXIS,ARG3)
DO 600 k=res_lo_ss(Z_AXIS), res_hi_ss(Z_AXIS)
DO 500 i3=arg_lo_ss(X_AXIS,ARG3), arg_hi_ss(X_AXIS,ARG3)
index_i = i - 1 + arg_2(i3,j3,k3,l3)
index_j = j - 1 + arg_1(i3,j3,k3,l3)
result(index_i,index_j,k,l) = arg_3(i3,j3,k3,l3)
500 CONTINUE
k3 = k3 + arg_incr(Z_AXIS,ARG3)
600 CONTINUE
l3 = l3 + arg_incr(T_AXIS,ARG3)
700 CONTINUE
* ^
* |
* USER CONFIGURABLE PORTION |
* **********************************************************************
RETURN
END
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