📄 gslib help declus.htm
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<H2>GSLIB Help Page: DECLUS</H2></CENTER>
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<STRONG>Description:</STRONG>
<UL>
<LI>Data are often spatially clustered; yet, we may need to have a histogram
that is representative of the entire area of interest. To obtain a
representative distribution, one approach is to assign declustering weights
whereby values in areas/cells with more data receive less weight than those
in sparsely sampled areas. The program declus provides an algorithm for
determining 3-D declustering weights in cases where the clusters are known
to be clustered preferentially in either high or low valued-areas. In other
cases, polygon-type declustering weights might be considered whereby the
weight is made proportional to the sample area (polygon) of influence.
<LI>The declustering weights output by declusare standardized so that they
sum to the number of data. A weight greater than 1.0 implies that the sample
is being overweighted and a weight lesser than 1.0 implies that the sample
is being downweighted (it is clustered with other samples). </LI></UL>
<DT><IMG height=14 alt=o src="GSLIB Help DECLUS.files/ball.red.gif" width=14>
<STRONG>Parameters:</STRONG>
<UL>
<LI><B>datafl:</B> a data file in simplified Geo-EAS format containing the
variable to be declustered.
<LI><B>icolx, icoly, icolz,</B> and <B>icolvr:</B> the column numbers for
the <I>x</I> <I>y</I> <I>z</I> coordinates and the variable.
<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>sumfl:</B> the output file containing all the attempted cell sizes
and the associated declustered mean values.
<LI><B>outfl:</B> file for PostScript output.
<LI><B>anisy</B> and <B>anisz:</B> the anisotropy factors to consider
rectangular cells. The cell size in the <I>x</I> direction is multiplied by
these factors to get the cell size in the <I>y</I> and <I>z</I> directions,
e.g., if a cell size of 10 is being considered and <B>anisy</B>2 and
<B>anisz</B>3 then the cell size in the <I>y</I> direction is 20 and the
cell size in the <I>z</I> direction is 30.
<LI><B>minmax:</B> an integer flag that specifies whether a minimum mean
value (<B>minmax</B>=0) or maximum mean value (<B>minmax</B>=1) is being
looked for.
<LI><B>ncell, cmin,</B> and <B>cmax:</B> the number of cell sizes to
consider, the minimum size, and the maximum size. Note that these sizes
apply directly to the <I>x</I> direction and the <B>anis</B> factors adjust
the sizes in the <I>y</I> and <I>z</I> directions.
<LI><B>noff:</B> the number of origin offsets. Each of the <B>ncell</B> cell
sizes are considered with <B>noff</B> different original starting points.
This avoids erratic results caused by extreme values falling into specific
cells. A good number is 4 in 2-D and 8 in 3-D. A short description of the
program </LI></UL></DT></DL><IMG height=8 alt=---
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