## GSLIB Help Page: BIGAUS

Description:

- This program allows checking for bivariate normality; a model of the normal scores variogram is input to `bigaus` The corresponding indicator semivariograms for specified cutoffs, lags, and directions are output from the program. The idea is to see how far the experimental indicator variograms deviate from those implied by the bivariate Gaussian distribution. A numerical integration algorithm is used to compute the Gaussian model-derived indicator variograms.

Parameters:

- outfl: the output file for the theoretical Gaussian indicator semivariograms. The format is the same as that created by the `gam` program; therefore, the program `vargplt` could be used to plot these indicator variograms.
- ncut: the number of thresholds.
- zc(ncut): ncut threshold values are required. These thresholds are expressed in units of cumulative probability, e.g., the lower quartile is 0.25, the median is 0.50. Note that the results are symmetric: the variogram for the 5th percentile (0.05) is the same as the 95th percentile (0.95).
- ndir and nlag: the number of directions and the number of lags to be considered.
- azm, dip and lag: for each of the ndir directions a direction must be specified by azm and dip and a unit lag offset must be specified (lag
- nst and c0: the number of structures and the nugget effect.
- For each of the nst nested structures one must define it the type of structure; 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.