bounds: in, optional, type=array
Set this keyword to a four-element array [xmin, ymin, xmax, ymax] containing the
grid limits of the output grid. If not provided, the grid limits are set to the extent
of the X and Y vectors.
double: in, optional, type=boolean, default=0
Set this keyword to perform all calculations in double precision floating point math.
Otherwise, the calculations are done in since precision floating point math.
exponential: in, optional, type=array
Set this keyword to a two- or three-element vector containing the kriging model parameters
[A, C0, C] for the kriging exponential model. The parameter A is the range. At distances beyond
A, the semivariogram or covariance remains essentially constant. The parameter C0 is the nugget.
Theoretically, a zero separation distance, the semivariogram model should be zero. But, sometimes
the semivariogram model displays a "lag" where the model function intercepts that Y axis at a
location other than zero. This is called the "nugget". The parameter C, if it is present, is the
value at which autocorrelation ceases to exist. If it is not present, it is calculated as the sample
variance. The value C0+C is called the sill, which is the variogram value for very large distances. One
of the kriging model keywords, `EXPONENTIAL` or `SPHERICAL`, must be used in the call to cgKrig2D.
For exponential models, the semivariagram at distance d is given as:
C(d) = C1 * Exp(-3 * (d/A) if d not equal 0.
C(d) = C1 + C0 if d equal 0.
gs: in, optional, type=array
A two-element array [xs, ys] giving the grid spacing of the output grid, where xs is the spacing
in the horizontal spacing between grid points, and ys is the vertical spacing. The default is
based on the extents of x and y. If the grid starts at x value xmin and ends at xmax, then the
default horizontal spacing is (xmax - xmin)/(`NX`-1). The ys parameter is computed in the same way.
The default grid size, if neither `NX` or `NY` are specified, is 51 by 51.
nx: in, optional, type=integer, default=51
The output grid size in the X direction. If not specified, it can be be inferred from the `GS`
and `BOUNDS` keywords. If not specified, and required by the code, a value of 51 is used.
ny: in, optional, type=integer, default=51
The output grid size in the Y direction. If not specified, it can be be inferred from the `GS`
and `BOUNDS` keywords. If not specified, and required by the code, a value of 51 is used.
regular: in, optional, type=boolean, default=0
Set this keyword to indicate the `Data` parameter is a 2D array containing measurements on a regular grid.
It is rare to set this keyword, as it is set automatically under many circumstances.
spherical: in, optional, type=array
Set this keyword to a two- or three-element vector containing the exponential model parameters
[A, C0, C] for the kriging spherical model. The parameter A is the range. At distances beyond
A, the semivariogram or covariance remains essentially constant. The parameter C0 is the nugget.
Theoretically, a zero separation distance, the semivariogram model should be zero. But, sometimes
the semivariogram model displays a "lag" where the model function intercepts that Y axis at a
location other than zero. This is called the "nugget". The parameter C, if it is present, is the
value at which autocorrelation ceases to exist. If it is not present, it is calculated as the sample
variance. The value C0+C is called the sill, which is the variogram value for very large distances. One
of the kriging model keywords, `EXPONENTIAL` or `SPHERICAL`, must be used in the call to cgKrig2D.
For spherical models, the semivariagram at distance d is given as:
C(d) = c0 + C * ( ( 1.5 * (d/a) ) - ( 0.5 * (d/a)^3) ) if d less than a.
C(d) = C + C0 if d greater than a.
C(d) = 0 if d equals 0.
xgrid: in, optional, type=array
Set this keyword to a two-element array, [xstart, xspacing] to indicate where the output grid starts
and what the horizontal spacing will be. Do not specify the `XVALUES` keyword if this keyword is used.
xvalues: in, optional, type=array
Set this keyword to a vector of X location values corresponding to the equivalent Z values in the `Data`
parameter. Do not use this keyword if using the `XGRID` keyword.
ygrid: in, optional, type=array
Set this keyword to a two-element array, [ystart, yspacing] to indicate where the output grid starts
and what the vertical spacing will be. Do not specify the `YVALUES` keyword if this keyword is used.
yvalues: in, optional, type=array
Set this keyword to a vector of Y location values corresponding to the equivalent Z values in the `Data`
parameter. Do not use this keyword if using the `YGRID` keyword.