NAME

       Areas_params - This document briefly describes all Areas parameters.

DESCRIPTION

       Areas currently supports nine parameters. These parameters are useful mostly for debugging
       Areas problems. The current values may be retrieved using one of the routines ARGETI or
       ARGETR. Parameter values may be reset using the routine ARSETI or ARSETR; the parameter
       'DI' is for retrieval only and may not be given a new value by the user.

       The Areas parameter descriptions appear below in alphabetical order. Each description
       begins with a line giving the parameter name and the intrinsic FORTRAN type of the
       parameter.

       'AL' - Real
              Arrowhead Length.  AL specifies the length of each arrowhead used on a debug plot
              produced by ARDBPA. The value is interpreted as a fraction of the width of the
              plotter frame. Using a value which is less than or equal to zero causes arrowheads
              to be omitted.  The default value is .008.

       'AT' - Integer
              Arithmetic Type flag.  AT allows the user to specify the type of arithmetic Areas
              is to use or to find out what type it decided to use.  A call to set the value of
              AT should precede any other call to an Areas routine (except, possibly, one to set
              the value of LC) and it should only be done once.  A call to get the value of AT
              will either return the value you set or a value picked by Areas.

              < 1  Areas decides what sort of arithmetic to use.

                1  Real arithmetic is to be used.

                2  Double-precision arithmetic is to be used.

                3  Multiple-precision arithmetic is to be used and Areas is to choose the base
                   value.

              > 3  Multiple-precision arithmetic is to be used and AT specifies the base value.
                   (For example, the value 100 specifies the use of base-100 multiple-precision
                   integer arithmetic.)

            Default: 0

            Note: You should use a nonzero value of AT only on the recommendation of an NCAR
            consultant.

       'AW' - Real
              Arrowhead Width.  AL specifies the half-width of each arrowhead used on a debug
              plot produced by ARDBPA. The value is interpreted as a fraction of the width of the
              plotter frame. Using a value which is less than or equal to zero causes arrowheads
              to be omitted.  The default value is .002.

       'DB' - Integer
              DeBug-plots flag. DB allows the user to study the area map.

                0  Debugging turned off. This is the default.

              > 0  Debugging is on. At selected break points, ARPRAM produces plots showing all
                   edge segments in the area map that belong to the edge group with group
                   identifier DB.

       'DC' - Integer
              Debug Colors index. ARDBPA uses color indices DC+1 through DC+5 for debug-plot
              colors.

              By default, DC=100, so ARDBPA defines and uses color indices 101 through 105.

       'DI' - Integer
              Direction Indicator flag. The value of DI is for retrieval only and cannot be set
              by the user.  A value returned for DI is meaningful only when the call to ARGETI
              that retrieves it originates from the user-written routine (dummy argument "APR")
              that is called by ARSCAM.  It then gives you information about the area whose
              polygonal boundary is defined by the values of APR's arguments. The two possible
              values of DI are:

              1    Edge of the area is given in counterclockwise order (with the interior to the
                   left).

              2    Edge of the area is given in clockwise order (with the interior to the right).

       'ID' - Real
              Identifier Distance.  ID specifies the distance from an arrow to a left or right
              area identifier on a debug plot produced by ARDBPA. The value is interpreted as a
              fraction of the width of the plotter frame. Using a value which is less than or
              equal to zero causes area identifiers to be omitted.  The default value is .004.

       'IS' - Real
              Identifier Size.  IS specifies the size of the characters used to write an area
              identifier on a debug plot produced by ARDBPA. The value is interpreted as a
              fraction of the width of the plotter frame. Using a value which is less than or
              equal to zero causes area identifiers to be omitted.  The default value is .001.

       'LC' - Integer
              Largest Coordinate. LC lets you specify the largest coordinate allowed in an area
              map. X and Y coordinates in an area map are represented by integers in the range
              from 0 to LC, inclusive; the default value of LC is 1000000.

              The minimum value allowed for LC is 1000; attempting to set LC<1000 gives it the
              value 1000. The value of LC must not be greater than the largest integer on the
              machine on which Areas is running; its value must also be exactly representable as
              a real number on that machine.

              A call to set the value of LC should precede any other call to an Areas routine and
              should only be done once.

       'RC' - Integer
              Reconciling Conflicts in area-identifier information.

              This is an array of 16 values, indexed by group identifier.  To set all values in
              the array to the same value "n", use "CALL ARSETI('RC',n)"; to set just the first
              value in the array, use "CALL ARSETI('RC(1)',n)"; to set just the second value, use
              "CALL ARSETI('RC(2)',n)"; and so on.  You can call ARGETI to get the value of RC(1)
              or RC(2) or RC(3), etc.; if you ask for the value of just RC, you will get the
              value of RC(1).

              RC(1) is associated with edge group 1, RC(2) with edge group 2, and so on.  An edge
              group with a group identifier greater than 16 is associated with RC(16).

              When the set of possible area identifiers for a given area in a given group is
              contradictory, some algorithm must be used to choose an identifier for the area.
              The value of that element of RC that is associated with the group determines what
              algorithm will be used, as follows:

              0    The default scheme: If any of the possible area identifiers is negative, use
                   -1 as the identifier for the area.  Otherwise, if none of the possible values
                   is non-zero, use a zero identifier.  Otherwise, from among the non-zero
                   possibilities, use the one most recently seen by AREAS.

              1    The set of possible identifiers is examined:  Zeroes are ignored, negatives
                   are treated as -1's, and the value that occurs most frequently in the
                   resulting set is used as the identifier for the area.

              2    Using RC = 2 is just like using RC = 1 except that zeroes are not ignored: the
                   area identifier used is simply the one that occurs most frequently in the set
                   of possibilities (all negatives being treated as -1's).

              -1   Using RC = -1 is just like using RC = 1 except that, if there are any
                   negatives in the set of possible identifiers, a -1 is used.

              -2   Using RC = -2 is just like using RC = 2 except that, if there are any
                   negatives in the set of possible identifiers, a -1 is used.

SEE ALSO

       Online: argeti, argetr, arseti, arsetr

       Hardcopy: NCAR Graphics Contouring and Mapping Tutorial

COPYRIGHT

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       University Corporation for Atmospheric Research
       The use of this Software is governed by a License Agreement.