Re: Calculating the area surrounded by a closed contour curve.
- To: mathgroup at smc.vnet.net
- Subject: [mg35927] Re: Calculating the area surrounded by a closed contour curve.
- From: "Allan Hayes" <hay at haystack.demon.co.uk>
- Date: Thu, 8 Aug 2002 06:06:17 -0400 (EDT)
- References: <aiqrui$4jf$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
For your example: cn=ContourPlot[x^2+y^2,{x,-1.5,1.5},{y,-1.5,1.5}, Contours->{1}] Express the contour lines as explicit line obects. gr=Graphics[cn] Extract the point lists from the lines lsts =Cases[gr,Line[pts_]:>pts, Infinity]; Code for area. ClosedLineArea[pts_] := (#1.RotateLeft[#2] - RotateLeft[#1].#2)&@@Transpose[pts]/2 Take the first, here the only, list of points and find the area. ClosedLineArea[lsts[[1]]] NOTE: in general you will have to deal many lines, some non-closed. -- Allan --------------------- Allan Hayes Mathematica Training and Consulting Leicester UK www.haystack.demon.co.uk hay at haystack.demon.co.uk Voice: +44 (0)116 271 4198 Fax: +44 (0)870 164 0565 "Jun Lin" <jl_03824 at yahoo.com> wrote in message news:aiqrui$4jf$1 at smc.vnet.net... > Does anybody know how to calculate the area surrounded by a closed > contour? For example, using ContourPlot[x^2+y^2, > {x,-1.5,1.5},{y,-1.5,1.5},Contours->{1}], I create a circular contour > of unity radius. How can I further calculate the area of the region > surrounded by the contour? Thanks very much for your help. > > Jun Lin >