GRID_3D Function

Returns a gridded, 2D array containing z values, given random x-, y-, z-coordinates (this function works best with sparse data points).

result = GRID_3D(points, grid_x, grid_y)

points A (3, n) array containing the random x, y, z points to be gridded.

grid_x The x dimension of the grid. The x values are scaled to fit this dimension.

grid_y The y dimension of the grid. The y values are scaled to fit this dimension.

result A gridded, 2D array containing z values.

Order The order of the weighting function to use for neighborhood averaging. Points are weighted by the function:

w = 1.0 / (dist ^ Order) 

where dist is the distance to the point. (Default: 2)

XMax The x-coordinate of the right edge of the grid. If omitted, maps the maximum x value found in the points(0, *) array to the right edge of the grid.

XMin The x-coordinate of the left edge of the grid. If omitted, maps the minimum x value found in the points(0, *) array to the left edge of the grid.

YMax The y-coordinate of the top edge of the grid. If omitted, maps the maximum y value found in the points(1, *) array to the top edge of the grid.

YMin The y-coordinate of the bottom edge of the grid. If omitted, maps the minimum y value found in the points(1, *) array to the bottom edge of the grid.

GRID_3D uses an inverse distance averaging technique to interpolate missing data values for 3D gridding. The gridded array returned by GRID_3D is suitable for use with the SURFACE, TV, and CONTOUR procedures.

GRID_3D is similar to FAST_GRID3. GRID_3D, however, works best with sparse data points (say, less than 1000 points to be gridded) and is stable when extrapolating into large void areas. (FAST_GRID3 works best with dense data points; it is considerably faster, but slightly less accurate, than GRID_3D.)

PRO grid_demo3

; This program shows 3D gridding with sparse data points.

points = INTARR(3, 10)
points(*, 0) = [1,1,2]
points(*, 1) = [1,1,3]
points(*, 2) = [9,9,5]
points(*, 3) = [9,8,0]
points(*, 4) = [4,9,6]
points(*, 5) = [0,9,9]
points(*, 6) = [3,7,15]
points(*, 7) = [5,6,-5]
points(*, 8) = [0,0,3]
points(*, 9) = [9,0,-1]

; Generate the data points.

zval = GRID_3D(points, 48, 32, Order=2.0)

; Grid the data points.

WINDOW, 0, Colors=128
SURFR
SURFACE, zval, Bottom=90, Ax=30.0, Az=30.0, /T3d

; Display the gridded data as a surface.

END

FAST_GRID2, FAST_GRID3, FAST_GRID4, GRID_2D, GRID_4D, GRID_SPHERE