📄 gslib help sisim.htm
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<H2>GSLIB Help Page: SISIM</H2></CENTER>
<DL>
<DT><IMG height=14 alt=o src="GSLIB Help SISIM.files/ball.red.gif" width=14>
<STRONG>Description:</STRONG>
<UL>
<LI>The <TT>sisim</TT> program is for the simulation of either integer-coded
categorical variables or continous variables with indicator data defined
from a cdf. </LI></UL>
<DT><IMG height=14 alt=o src="GSLIB Help SISIM.files/ball.red.gif" width=14>
<STRONG>Parameters:</STRONG>
<UL>
<LI><B>vartype:</B> the variable type (1=continuous, 0=categorical)
<LI><B>ncat:</B> the number of thresholds or categories
<LI><B>cat:</B> the threshold values or category codes (there should be
<B>ncat</B> values on this line of input)
<LI><B>pdf:</B> the global cdf or pdf values (there should be <B>ncat</B>
values on this line of input)
<LI><B>datafl:</B> the input data in a simplified Geo-EAS file.
<LI><B>icolx, icoly, icolz,</B> and <B>icolvr:</B> the column numbers for
the <I>x,y,</I> and <I>z</I> coordinates and the variable to be simulated.
One or two of the coordinate column numbers can be set to zero which
indicates that the simulation is 2-D or 1-D.
<LI><B>directik:</B> already transformed indicator values are read from this
file. Missing values are identified as less than <B>tmin</B> 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.
<LI><B>icolx, icoly, icolz,</B> and <B>icoli:</B> the columns for the <I>x,
y,</I> and <I>z</I> coordinates, and the indicator variables.
<LI><B>imbsim:</B> set to 1 if considering Markov-Bayes option for cokriging
with soft indicator data, otherwise, set to 0.
<LI><B>b(z):</B> if <B>imbsim</B> is set to 1, then the <I>B(z)</I>
calibration values are needed.
<LI><B>tmin</B> and <B>tmax:</B> all values strictly less than <B>tmin</B>
and strictly greater than <B>tmax</B> are ignored.
<LI><B>zmin</B> and <B>zmax:</B> minimum and maximum attribute values when
considering a continuous variable
<LI><B>ltail</B> and <B>ltpar</B> specify the extrapolation in the lower
tail: <B>ltail</B>=1 implements linear interpolation to the lower limit
<I>z_min</I> <B>ltail</B>=2 power model interpolation, with <B>w=ltpar</B>
to the lower limit <B>zmin</B> and <B>ltail</B>=3 implements linear
interpolation between tabulated quantiles (only for continuous variables).
<LI><B>middle</B> and <B>midpar</B> specify the interpolation within the
middle of the distribution: <B>middle</B>=1 implements linear interpolation;
<B>middle</B>=2 implements power model interpolation, with <B>w=midpar</B>
and <B>middle</B>=3 allows for linear interpolation between tabulated
quantile values (only for continuous variables).
<LI><B>utail</B> and <B>utpar</B> specify the extrapolation in the upper
tail of the distribution: <B>utail</B>=1 implements linear interpolation to
the upper limit <B>zmax</B>, <B>utail</B>=2 implements power model
interpolation, with <B>w=utpar</B>, to the upper limit <B>zmax</B>
<I>utail=3</I> implements linear interpolation between tabulated quantiles,
and <B>utail</B>=4 implements hyperbolic model extrapolation with
<B>w=utpar</B> The hyperbolic tail extrapolation is limited by <B>zmax</B>
(only for continuous variables).
<LI><B>tabfl:</B> If linear interpolation between tabulated values is the
option selected for any of the three regions then this simplified Geo-EAS
format file is opened to read in the values. One legitimate choice is
exactly the same file as the conditioning data, i.e., <B>datafl</B> Note
that <B>tabfl</B> specifies the tabulated values for all classes.
<LI><B>icolvrt</B> and <B>icolwtt:</B> the column numbers for the values and
declustering weights in <B>tabfl</B> Note that declustering weights can be
used but are not required - just set the column number less than or equal to
zero. If declustering weights are not used, then the class probability is
split equally between the sub-classes defined by the tabulated values.
<LI><B>idbg:</B> an integer debugging level between 0 and 3. The larger the
debugging level the more information written out.
<LI><B>dbgfl:</B> the file for the debugging output.
<LI><B>outfl:</B> the output grid is written to this file. The output file
will contain the results, cycling fastest on <I>x</I> then <I>y</I> then
<I>z</I> then simulation by simulation.
<LI><B>nsim:</B> the number of simulations to generate.
<LI><B>nx, xmn, xsiz:</B> definition of the grid system (<I>x</I> axis).
<LI><B>ny, ymn, ysiz:</B> definition of the grid system (<I>y</I> axis).
<LI><B>nz, zmn, zsiz:</B> definition of the grid system (<I>z</I> axis).
<LI><B>seed:</B> random number seed (a large odd integer).
<LI><B>ndmax:</B> the maximum number of original data that will be used to
simulate a grid node.
<LI><B>ncnode:</B> the maximum number of previously simulated nodes to use
for the simulation of another node.
<LI><B>maxsec:</B> the maximum number of soft data (at node locations) that
will be used for the simulation of a node. This is particularly useful to
restrict the number of soft data when an exhaustive secondary variable
informs all grid nodes.
<LI><B>sstrat:</B> if set to 0, the data and previously simulated grid nodes
are searched separately: the data are searched with a super block search and
the previously simulated nodes are searched with a spiral search. If set to
1, the data are relocated to grid nodes and a spiral search is used; the
parameters <B>ndmin</B> and <B>ndmax</B> are not considered.
<LI><B>multgrid:</B> a multiple grid simulation will be performed if this is
set to 1 (otherwise a standard spiral search will be considered).
<LI><B>nmult:</B> the target number of multiple grid refinements to consider
(used only if <B>multgrid</B> is set to 1).
<LI><B>noct:</B> the number of original data to use per octant. If this
parameter is set less than or equal to 0, then it is not used; otherwise,
the closest <B>noct</B> data in each octant are retained for the simulation
of a grid node.
<LI><B>radius_hmax</B>, <B>radius_hmin</B> and <B>radius_vert</B>: the
search radii in the maximum horizontal direction, minimum horizontal
direction, and vertical direction (see angles below).
<LI><B>sang1, sang2</B> and <B>sang3:</B> the angle parameters that describe
the orientation of the search ellipsoid. See the discussion
<LI><B>mik</B> and <B>mikcat:</B> if <B>mik</B> is set to 0, then a full
indicator kriging is performed at each grid node location to establish the
conditional distribution. If <B>mik</B> is set to 1, then the median
approximation is used, i.e., a single variogram is used for all categories;
therefore, only one kriging system needs to be solved and the computer time
is significantly reduced. The variogram corresponding to category
<B>mikcat</B> will be used.
<LI><B>ktype:</B> the kriging type (0 = simple kriging, 1 = ordinary
kriging) used throughout the loop over all nodes. SK is required by theory,
only in cases where the number of original data found in the neighborhood is
large enough can OK be used without the risk of spreading data values beyond
their range of influence. The global pdf values (specified with each
category) are used for simple kriging. </LI></UL>The following set of
parameters are required for each of the <B>ncat</B> categories:
<UL>
<LI><B>nst,</B> and <B>c0:</B> the number of semivariogram structures and
the isotropic nugget constant.
<LI>For each of the <B>nst</B> nested structures one must define <B>it</B>
the type of structure; <B>cc</B> the <I>c</I> parameter;
<B>ang1,ang2,ang3</B> the angles defining the geometric anisotropy;
<B>aa_hmax</B>, the maximum horizontal range; <B>aa_hmin</B>, the minimum
horizontal range; and <B>aa_vert</B>, the vertical range. Each semivariogram
model refers to the corresponding indicator transform. A Gaussian variogram
with a small nugget constant is not a legitimate variogram model for a
discontinuous indicator function. There is no need to standardize the
parameters to a sill of one since only the relative shape affects the
kriging weights. </LI></UL></DT></DL><IMG height=8 alt=---
src="GSLIB Help SISIM.files/line.blue.gif" width=652>
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