Graph convex hulls                                              [STB-23: gr16]
------------------

    ^condraw^ varlist^,^ ^gr^no^(^#^)^ ^h^ull^(^#^)^ [ ^d^r^(^str^)^ ^g^roup^(^str^)^ ^v^id^(^str^)^ ]

graphs the convex hulls generated by the ^conhull^ ado-file.  The varlist
contains the names of the variables containing the x and y coordinates of
points and the name of the variable containing the convex hull number. ^condraw^
generates new variables for graphing the hulls and adds new observations so
Stata can connect the points on the hull.  After the graph is displayed, the
user can redraw the graph with different options and/or save it.  

There are three ways to use ^condraw^:

1. ^condraw x y conhull^ assumes that ^conhull^ generated one or more hulls
   for the entire set of points and placed them in the variable ^conhull^.
   Since the ^hull()^ is not specified, the outermost convex hull is graphed.
   The command ^condraw y conhull, hu(2)^ graphs the second hull.

2. ^condraw x y conhull, gr(smoke)^ assumes that ^conhull^ generated one or
   more hulls for each class of the categorical variable ^smoke^.  Without the
   ^hull()^ option, the outermost hull for each class is graphed. The command
   ^condraw x y conhull, g(smoke) h(3)^ graphs the third hull for each class
   of the categorical variable.

3. ^condraw x y conhull, g(smoke) gr(2) h(2)^ assumes that ^conhull^ generated
   one or more hulls for each class of the categorical variable ^smoke^, but the
   user desires to graph only the second outermost hull for the second level
   of ^smoke^.  

Note that using ^condraw x y conhull^ on a data set for which ^conhull^ generated
hulls for each class of a categorical variable will produce a graph in which
the points are not connected properly.


Options
-------

^d^r^(^str^)^ names a marker variable that allows the points in the graph to
   be closed.  The default is ^dr^.  As this is not a temporary variable
   a ^dr already defined^ error message will appear if you use the default
   and your data set contains a variable named ^dr^.

^gr^no^(^#^)^ specifies which class of the categorical variable identified
   by ^g^roup(str) is to be used in the graph.  The default is to use all
   classes.  If more than one, but fewer than all, classes are desired the
   user should use the default option and then eliminate the undesired
   classes when regraphing the data.

^g^roup^(^str^)^ is the name of a categorical variable for which convex hulls
   were generated.  The default is to assume the entire sample was used to
   generate the hulls.

^h^ull^(^#^)^ specifies the hull to be graphed.  The default is to graph the 
   outermost hull.

^v^id^(^str^)^ names the new variables needed for graphing the hulls.  The default
   is ^hv*^.  ^condraw x y,g(smoke) h(3)^ graphs the third outermost hull for the
   levels of the categorical variable ^smoke^.  If ^smoke^ has three levels three
   new variables are created: ^hv1^ ^hv2^ ^hv3^.  As these are not temporary
   variables, an ^hv1 already defined^ error message will appear if you use the
   default and your data set contains a variable named ^hv1^.


Authors
------

        J. Patrick Gray
        Department of Anthropology
        University of Wisconsin-Milwaukee
        Milwaukee, WI 53201
	jpgray@@alpha1.csd.uwm.edu

        Tim McGuire
        Pillsbury College
        Owatonna, MN 55060


Also see
--------

    STB:  gr16 (STB-23)
On-line:  ^help^ for @conhull@