NCL Home > Documentation > Functions > Interpolation

dsgrid3

Interpolates data from an unstructured (randomly-spaced) grid to a 3D grid using inverse distance weighted interpolation.

Prototype

	function dsgrid3 (
		x  [*] : numeric,  
		y  [*] : numeric,  
		z  [*] : numeric,  
		u      : numeric,  
		xo [*] : numeric,  
		yo [*] : numeric,  
		zo [*] : numeric   
	)

	return_val [dimsizes(x) * dimsizes(y) * dimsizes(z)] :  float or double

Arguments

x

A 1D array of length npts containing the X coordinates of the input data.

y

A 1D array of length npts containing the Y coordinates of the input data.

z

A 1D array of length npts containing the Z coordinates of the input data.

u

An array of any dimensionality (last dimension must be npts) containing the functional values of the input data. Element u(...,i) is the value of the input function at coordinate (x(i), y(i), z(i)) for i = 0, npts - 1).

xo

A 1D array of any length (numxout) containing the X coordinates of the output data grid. The values in xo must be increasing, but need not be equally spaced.

yo

A 1D array of any length (numyout) containing the Y coordinates of the output data grid. The values in yo must be increasing, but need not be equally spaced.

zo

A 1D array of any length (numzout) containing the Z coordinates of the output data grid. The values in zo must be increasing, but need not be equally spaced.

Return value

Returns a floating point array dimensioned as N x numxout x numyout x numzout, where N represents all but the last dimension of u. The return value type is double if u is of type double.

Description

This function interpolates data from an unstructured (randomly-spaced) grid to a 3D grid.

This function requires that desired values for control parameters have been set using the procedure dssetp.

This function is part of the Dsgrid package which implements a simple inverse distance weighted interpolation algorithm. No missing values are allowed.

See Also

dsgrid2, dspnt2, dspnt3, dsgetp, dssetp

Examples

begin

  NUM = 1000
  NX  = 21
  NY  = 21
  NZ  = 21
  RAND_MAX = 32767.0

  xi = new((/NUM/), float)
  yi = new((/NUM/), float)
  zi = new((/NUM/), float)
  u  = new((/NUM/), float)

  xo = new((/NX/), float)
  yo = new((/NY/), float)
  zo = new((/NZ/), float)

  xmin = -2.0
  ymin = -2.0
  zmin = -2.0
  xmax =  2.0
  ymax =  2.0
  zmax =  2.0

;
; Create random data in three space and define a function.
;
  rand1 = new((/NUM/), float)
  rand2 = new((/NUM/), float)
  rand3 = new((/NUM/), float)
  srand(1)
  do i = 0,NUM - 1
    rand1(i) = rand
    rand2(i) = rand
    rand3(i) = rand
  end do
  xi = xmin + (xmax - xmin) * (rand1 / RAND_MAX)
  yi = ymin + (ymax - ymin) * (rand2 / RAND_MAX)
  zi = zmin + (zmax - zmin) * (rand3 / RAND_MAX)

  u = (xi * xi) + (yi * yi) + (zi * zi)
;
; Create the output grid.
;
  ii = fspan(0, 20.0, 21)
  xo = xmin + (ii / (NX - 1)) * (xmax - xmin)
  yo = ymin + (ii / (NY - 1)) * (ymax - ymin)
  zo = zmin + (ii / (NZ - 1)) * (zmax - zmin)

;
; Interpolate.
;
  u = dsgrid3(xi, yi, zi, u, xo, yo, zo)

end