## File: inside.pro

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coyote 2019.01.29-1
 `123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131` ``````;+ ; NAME: ; INSIDE ; ; PURPOSE: ; ; The purpose of this function is to indicate whether a specified ; 2D point is inside (returns a 1) a specified 2D polygon or outside ; (returns a 0). ; ; AUTHOR: ; ; FANNING SOFTWARE CONSULTING ; David Fanning, Ph.D. ; 1645 Sheely Drive ; Fort Collins, CO 80526 USA ; Phone: 970-221-0438 ; E-mail: david@idlcoyote.com ; Coyote's Guide to IDL Programming: http://www.idlcoyote.com/ ; ; CATEGORY: ; ; Utility. ; ; CALLING SEQUENCE: ; ; result = INSIDE(x, y, xpts, ypts) ; ; INPUTS: ; ; x: A scalar or vector of the x coordinates of the 2D point(s) to check. ; y: A scalar or vector of the y coordinates of the 2D point(s) to check. ; xpts: The x coordinates of the 2D polygon. ; ypts: The y coordinates of the 2D polygon. ; ; OUTPUTS: ; ; result: A scalar or vector set to 1 if the point is inside the polygon and to ; 0 if the point is outside the polygon. ; ; KEYWORDS: ; ; INDEX: An output keyword. If set to a named variable, will return the indices ; of the X and Y points that are inside the polygon. ; ; ALGORITHM: ; ; Based on discussions on the IDL newsgroup (comp.lang.idl-pvwave) and ; discussed here: ; ; http://www.idlcoyote.com/tips/point_in_polygon.html ; ; Primarily the work of B�rd Krane and William Connelly. ; ; MODIFICATION HISTORY: ; ; Written by: David W. Fanning, 4 September 2003. ; Vectorized the function in accord with William Connelly's suggestions 24 July 2005. DWF. ;- ;******************************************************************************************; ; Copyright (c) 2008, by Fanning Software Consulting, Inc. ; ; All rights reserved. ; ; ; ; Redistribution and use in source and binary forms, with or without ; ; modification, are permitted provided that the following conditions are met: ; ; ; ; * Redistributions of source code must retain the above copyright ; ; notice, this list of conditions and the following disclaimer. ; ; * Redistributions in binary form must reproduce the above copyright ; ; notice, this list of conditions and the following disclaimer in the ; ; documentation and/or other materials provided with the distribution. ; ; * Neither the name of Fanning Software Consulting, Inc. nor the names of its ; ; contributors may be used to endorse or promote products derived from this ; ; software without specific prior written permission. ; ; ; ; THIS SOFTWARE IS PROVIDED BY FANNING SOFTWARE CONSULTING, INC. ''AS IS'' AND ANY ; ; EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES ; ; OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT ; ; SHALL FANNING SOFTWARE CONSULTING, INC. BE LIABLE FOR ANY DIRECT, INDIRECT, ; ; INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED ; ; TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; ; ; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ; ; ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT ; ; (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS ; ; SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. ; ;******************************************************************************************; FUNCTION Inside, x, y, xpts, ypts, INDEX=index On_Error, 1 sx = Size(xpts) sy = Size(ypts) IF (sx[0] EQ 1) THEN NX=sx[1] ELSE Message, 'X coordinates of polygon not a vector.' IF (sy[0] EQ 1) THEN NY=sy[1] ELSE Message, 'Y coordinates of polygon not a vector.' IF (NX EQ NY) THEN N = NX ELSE Message, 'Incompatable vector dimensions.' ; Close the polygon. tmp_xpts = [xpts, xpts[0]] tmp_ypts = [ypts, ypts[0]] ; Set up counters. i = indgen(N) ip = indgen(N)+1 nn = N_Elements(x) X1 = tmp_xpts(i) # Replicate(1,nn) - Replicate(1,n) # Reform([x],nn) Y1 = tmp_ypts(i) # Replicate(1,nn) - Replicate(1,n) # Reform([y],nn) X2 = tmp_xpts(ip) # Replicate(1,nn) - Replicate(1,n) # Reform([x],nn) Y2 = tmp_ypts(ip) # Replicate(1,nn) - Replicate(1,n) # Reform([y],nn) ; Calculate the dot and cross products of the point to neighboring points in the polygon. ; Calculate the tangent of the angle between the two nearest adjacent points. If the point ; is outside the polygon, then summing over all possible angles will give a small number, ; in this case less than an arbitrary 0.1. dp = X1*X2 + Y1*Y2 ; Dot-product cp = X1*Y2 - Y1*X2 ; Cross-product theta = Atan(cp,dp) ret = Replicate(0L, N_Elements(x)) i = Where(Abs(Total(theta,1)) GT 0.01, count) IF (count GT 0) THEN ret(i)=1 ; Make this a scalar value if there is only one value. IF (N_Elements(ret) EQ 1) THEN ret=ret[0] ; If the index keyword is set, then return indices. IF (Arg_Present(index)) THEN ret=(Indgen(/Long, N_Elements(x)))(Where(ret eq 1)) RETURN, ret END ``````