Identifies the input and output map data
sets.
Requirements: |
An input map data set is required.
|
PROC GREMOVE <DATA=input-map-data-set>
<FUZZ=fuzz-factor>
<OUT=output-map-data-set>
<NODECYCLE>;
|
-
DATA=input-map-data-set
-
specifies the map data set that is to be
processed. By default, the procedure uses the most recently created SAS data
set. The GREMOVE procedure expects the observations in the input map data
set to be sorted in ascending order of the BY-variable values.
- FUZZ=fuzz-factor
-
specifies a tolerance for possible error in the data. This
allows for points that are very close but not quite equal to be considered
as the same point. The fuzz-factor can be any non-negative number. A fuzz-factor
of 0.0 would indicate that the points have to be exactly the same. The unit
represented by the fuzz-factor (degrees, radians, feet, meters, kilometers,
miles) is the same as that represented by the X and Y values of the points.
The error is computed the same in both X and Y directions using the
following formula:
Point_is_equal = (ABS(x1 - x2) <= fuzz-factor) && (ABS(y1 - y2) <= fuzz-factor)
- NODECYCLE | NC
-
tells PROC GREMOVE to use a topological algorithm for closing
the resulting polygons. By default, PROC GREMOVE simply removes internal
boundaries without using any polygon information. This might cause errors
in closing the resulting polygons in certain cases--specifically when
two resulting polygons intersect at a single point. Using a topological algorithm
allows PROC GREMOVE to traverse the resulting polygons for proper closure
of the polygons. When the single point intersection is encountered, the algorithm
uses the topology to correctly interpret which existing segment to choose
in closing the polygon. The use of NODECYCLE, thus, requires that the data
be topologically correct (that is, polygons do not overlap themselves or each
other and there are no anomalies in the boundaries such as a repeated series
of points).
Certain SAS/GRAPH procedures, such as PROC GREDUCE, which have no knowledge
of topology and do not maintain topology, can produce topologically incorrect
polygons. Therefore, it is recommended that you not use PROC GREDUCE if you
are going to use PROC GREMOVE with NODECYCLE specified.
-
OUT=output-data-set
-
names the new map data set, which contains
the coordinates of the new unit areas created by the GREMOVE procedure. By
default, the GREMOVE procedure names the new data set using the DATAn naming convention. That is, the procedure uses the name WORK.DATAn,
where n is the next unused
number in sequence. Thus, the first automatically named data set is DATA1,
the second is DATA2, and so on.
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Copyright © 2010 by SAS Institute Inc., Cary, NC, USA. All rights reserved.