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<HTML>
<HEAD>
<TITLE>POLYGON command</TITLE>
</HEAD>
<BODY BGCOLOR="#FFFFFF" TEXT="#000000">
<P><font size="+3" color="green"><B>POLYGON command</B></font></P>
<TABLE border="1" width="572">
<TR>
<TD width="15%" valign="top"><B>Syntax</B>:</TD>
<TD width="85%" valign="top"><CODE>
POLYGON xpoly ypoly xdata ydata key</CODE>
</TD></TR>
<TR>
<TD valign="top"><B>Qualifiers:</B></TD>
<TD valign="top"><CODE>
\INSIDE, \OUTSIDE</CODE>
</TD></TR>
<TR>
<TD valign="top"><B>Defaults:</B></TD>
<TD valign="top"><CODE>
\INSIDE</CODE>
</TD></TR>
</TABLE>
<P>
The <CODE>POLYGON</CODE> command creates a vector, <CODE>key</CODE>, which will have the same
length as the input vectors, <CODE>xdata</CODE> and <CODE>ydata</CODE>. By default,
<CODE>key[i] = 1</code> if the point <code>(xdata[i],ydata[i])</code> is inside
the polygon defined by input vectors <CODE>xpoly</CODE> and <CODE>ypoly</CODE>, otherwise
<CODE>key[i] = 0</code>. If the <CODE>\OUTSIDE</CODE> qualifier is used,
<CODE>key[i] = 0</code> if the point <code>(xdata[i],ydata[i])</code>
is inside the polygon, otherwise <CODE>key[i] = 1</code>.</p>
<p>
<font size="+1" color="green">Example</font></p>
<p>
<font color="blue"><pre>
GENERATE\RANDOM X -5 5 2000 ! generate some "data"
GENERATE\RANDOM Y 10 20 2000 !
WINDOW 5 !
SET PLOTSYMBOL -11 ! choose unjoined point plotting symbol
GRAPH X Y ! display the data graphically
XP = {-0.5;1.2;-0.2;1.3;-3;-2} ! the polygon vertices
YP = {13;13.5;16;18.5;18;14} !
POLYGON\OUTSIDE XP YP X Y K !! find data points outside polygon, create key vector, K
WINDOW 7 !
SET PLOTSYMBOL -11 ! choose unjoined point plotting symbol
IDX = WHERE(K=1) ! choose indices of points outside polygon
GRAPH X[IDX] Y[IDX] ! display data without unwanted points
SET PLOTSYMBOL 0 ! choose no plotting symbol
GRAPH\OVERLAY XP//{-0.5} YP//{13} ! overlay the polygon (close by appending first point)
</PRE></font></P>
<p>
<center><IMG SRC="polygon.png"></center></p>
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</HTML>
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