## GSLIB Help Page: IK3D

Description:

- The program `ik3d` considers ordinary or simple indicator kriging of either categorical and cdf-type indicators, it performs all order relation corrections, and, optionally, allows the direct input of already transformed indicator data, including possibly soft data and constraint intervals.

Parameters:

- vartype: the variable type (1=continuous, 0=categorical)
- ncat: the number of thresholds or categories
- cat: the thresholds or categories (there should be ncat values on this line of input)
- pdf: the global cdf or pdf values (there should be ncat values on this line of input)
- datafl: the input continuous data in a simplified Geo-EAS formatted file.
- icolx, icoly, icolz, and icolvr: the columns for the x, y, and z coordinates, and the continuous variable to be estimated.
- directik: already transformed indicator values are read from this file. Missing values are identified as less than tmin which would correspond to a constraint interval. Otherwise, the cdf data should steadily increase from 0 to 1 and soft categorical probabilities must be between 0 to 1 and sum to 1.0.
- icolx, icoly, icolz, and icoli: the columns for the x, y, and z coordinates, and the indicator variables.
- tmin and tmax: all values strictly less than tmin and greater than or equal to tmax are ignored.
- idbg: an integer debugging level between 0 and 3. The higher the debugging level the more output.
- dbgfl: the debugging output is written to this file.
- outfl: the output grid is written to this file. The output file will contain the order relation corrected conditional distributions for all nodes in the grid. The conditional probabilities or ccdf values will be written to the same line or ``record''; there are ncat variables in the output file. Unestimated nodes are identified by all ccdf values equal to -9.9999.
- nx, xmn, xsiz: definition of the grid system (x axis).
- ny, ymn, ysiz: definition of the grid system (y axis).
- nz, zmn, zsiz: definition of the grid system (z axis).
- ndmin and ndmax: the minimum and maximum number of data points to use for kriging a block.
- radius_hmax radius_hmin and radius_vert the search radii in the maximum horizontal direction, minimum horizontal direction, and vertical direction (see angles below).
- sang1, sang2 and sang3: the angle parameters that describe the orientation of the search ellipsoid. See the discussion on anisotropy specification associated with Figure II.4.
- noct: the maximum number of samples per octant (octant search is not used if noct=0
- mik and mikcut: If mik=0, then a full IK is performed. If mik=1, then a median IK approximation is performed where the kriging weights from the category or cutoff closest to mikcut are used for all cutoffs.
- ktype: simple kriging is performed if ktype=0 ordinary kriging is performed if ktype=1

A variogram is is required for each of the ncat thresholds/categories:

- nst, and c0: the number of variogram structures and the nugget constant, for the corresponding indicator variogram.
- For each of the nst nested structures one must define it the type of structure (the power model is not allowed); cc the c parameter; ang1,ang2,ang3 the angles defining the geometric anisotropy; aa_hmax the maximum horizontal range; aa_hmin the minimum horizontal range; and aa_vert the vertical range. A detailed description of these parameters is given in section II.3. A short description of the program