# coyote: INSIDE

- coyote/Utilities
- [Source code]

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.