nngetslopes, nngetsloped

Routines that retrieve a slope at a specified coordinate value. These routines are part of the Natgrid package which implements a natural neighbor interpolation method.

Synopsis

    function nngetslopes(
        i[1] : integer,
        j[1] : integer
    )

    function nngetsloped(
        i[1] : integer,
        j[1] : integer
    )

Arguments

i: a subscript indexing the first dimensioned variable in the output grid of the most recent call to natgrids(d)
j: a subscript indexing the second dimensioned variable in the output grid of the most recent call to natgrids(d)

Description

Both the nngetslopes and nngetsloped functions return a slope (as a scalar float value) at the grid point z(i,j) where z is the output grid in the most recent call to natgrids(d). nngetslopes is the single precision version and nngetsloped is the double precision version.

Example

begin
;
; Define constants
;
  RAD2DEG = 57.29578
  NUMXOUT = 21
  NUMYOUT = 21
;
;  Coordinate data are defined as random numbers between
;  -0.2 and 1.2. and are explicitly defined here for uniformity
;  across platforms.
; 
  x = (/ 1.16,  0.47,  0.29,  0.72,  0.52,  1.12,  0.33,  0.20,  0.30, \
 0.78,  0.92,  0.52,  0.44,  0.22, -0.10,  0.11,  0.59,  1.13, \
 0.68,  1.11,  0.93,  0.29,  0.74,  0.43,  0.87,  0.87, -0.10, \
 0.26,  0.85,  0.00, -0.02,  1.01, -0.12,  0.65,  0.39,  0.96, \
 0.39,  0.38,  0.94, -0.03, -0.17,  0.00,  0.03,  0.67, -0.06, \
 0.82, -0.03,  1.08,  0.37,  1.02, -0.11, -0.13,  1.03,  0.61, \
 0.26,  0.18,  0.62,  0.42,  1.03,  0.72,  0.97,  0.08,  1.18, \
 0.00,  0.69,  0.10,  0.80,  0.06,  0.82,  0.20,  0.46,  0.37, \
 1.16,  0.93,  1.09,  0.96,  1.00,  0.80,  0.01,  0.12,  1.01, \
 0.48,  0.79,  0.04,  0.42,  0.48, -0.18,  1.16,  0.85,  0.97, \
 0.14,  0.40,  0.78,  1.12,  1.19,  0.68,  0.65,  0.41,  0.90, \
 0.84, -0.11, -0.01, -0.02, -0.10,  1.04,  0.58,  0.61,  0.12, \
-0.02, -0.03,  0.27,  1.17,  1.02,  0.16, -0.17,  1.03,  0.13, \
 0.04, -0.03,  0.15,  0.00, -0.01,  0.91,  1.20,  0.54, -0.14, \
 1.03,  0.93,  0.42,  0.36, -0.10,  0.57,  0.22,  0.74,  1.15, \
 0.40,  0.82,  0.96,  1.09,  0.42,  1.13,  0.24,  0.51,  0.60, \
 0.06,  0.38,  0.15,  0.59,  0.76,  1.16,  0.02,  0.86,  1.14, \
 0.37,  0.38,  0.26,  0.26,  0.07,  0.87,  0.90,  0.83,  0.09, \
 0.03,  0.56, -0.19,  0.51,  1.07, -0.13,  0.99,  0.84,  0.22/)

  y = (/ -0.11,  1.07,  1.11, -0.17,  0.08,  0.09,  0.91,  0.17, -0.02, \
  0.83,  1.08,  0.87,  0.46,  0.66,  0.50, -0.14,  0.78,  1.08, \
  0.65,  0.00,  1.03,  0.06,  0.69, -0.16,  0.02,  0.59,  0.19, \
  0.54,  0.68,  0.95,  0.30,  0.77,  0.94,  0.76,  0.56,  0.12, \
  0.05, -0.07,  1.01,  0.61,  1.04, -0.07,  0.46,  1.07,  0.87, \
  0.11,  0.63,  0.06,  0.53,  0.95,  0.78,  0.48,  0.45,  0.77, \
  0.78,  0.29,  0.38,  0.85, -0.10,  1.17,  0.35,  1.14, -0.04, \
  0.34, -0.18,  0.78,  0.17,  0.63,  0.88, -0.12,  0.58, -0.12, \
  1.00,  0.99,  0.45,  0.86, -0.15,  0.97,  0.99,  0.90,  0.42, \
  0.61,  0.74,  0.41,  0.44,  1.08,  1.06,  1.18,  0.89,  0.74, \
  0.74, -0.06,  0.00,  0.99,  0.03,  1.00, -0.04,  0.24,  0.65, \
  0.12,  0.13, -0.09, -0.05,  1.03,  1.07, -0.02,  1.18,  0.19, \
  0.03, -0.03,  0.86,  1.12,  0.38,  0.72, -0.20, -0.08, -0.18, \
  0.32,  0.13, -0.19,  0.93,  0.81,  0.31,  1.09, -0.03,  1.01, \
 -0.17,  0.84, -0.11,  0.45,  0.18,  0.23,  0.81,  0.39,  1.09, \
 -0.05,  0.58,  0.53,  0.96,  0.43,  0.48,  0.96, -0.03,  1.13, \
  1.16,  0.16,  1.15,  0.57,  0.13,  0.71,  0.35,  1.04,  0.62, \
  1.03,  0.98,  0.31,  0.70,  0.97,  0.87,  1.14,  0.08,  1.19, \
  0.88,  1.00,  0.51,  0.03,  0.17,  1.01,  0.44,  0.17, -0.11/)

  z = (x-0.25)*(x-0.25) + (y-0.50)*(y-0.50)

  u = new((/NUMXOUT,NUMYOUT/),float)
  v = new((/NUMXOUT,NUMYOUT/),float)

  xc = 1./(NUMXOUT-1.) 
  xo = ispan(0,NUMXOUT-1,1) * xc

  yc = 1./(NUMYOUT-1.) 
  yo = ispan(0,NUMXOUT-1,1) * yc
;
;  Turn on gradient estimate calculations, flag calculation of
;  aspects and slopes, set flag to return aspects and slopes in
;  radians.
;
  nnsetp("SDI - compute slopes and aspects",1)
  nnsetp("IGR - use gradient estimates",1)
  nnsetp("RAD - return results in radians",1)
;
;  Do the interpolation.
;
  out = natgrids(x, y, z, xo, yo)
;
;  Get the aspects.
;
  do i=0,NUMXOUT-1
    do j=0,NUMYOUT-1
       rtmp = nngetaspects(i,j)
       u(i,j) = sin(rtmp)
       v(i,j) = cos(rtmp)
    end do
  end do

;
;  Get the slopes.
;
  do i = 0,NUMXOUT-1
    do j = 0,NUMYOUT-1
      rtmp = nngetslopes(i, j);
      u(i,j) = RAD2DEG*rtmp
    end do
  end do
end

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$Revision: 1.7 $ $Date: 1998/11/11 23:32:21 $