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From: Khalid on 1 Nov 2009 07:49
hi there!!

I plotted heat contours on (x,y) plane, I wud like to know the area covered by each contour is that possible?
Thanks
From: ImageAnalyst on 1 Nov 2009 08:30
On Nov 1, 7:49 am, "Khalid " <khabu...(a)hotmail.com> wrote:
> hi there!!
>
> I plotted heat contours on (x,y) plane, I wud like to know the area covered by each contour is that possible?
> Thanks

------------------------------------------------------------------------------------------------
How about using the polyarea() function?
From: Khalid on 1 Nov 2009 08:52
Thank you ImageAnalyst for your reply. as you might see I am new to matlab. the plotting i did is as following:
figure (1)
[c,h]=contourf(xg,yg,irw,40);
% clabel(c,h);
colorbar;
xlabel('PI * DA');
ylabel('THA');
grid
do i just need to add the function polyarea(x,y) to it and it will calculate the area of each contour?
I appreciate your time and help

ImageAnalyst <imageanalyst(a)mailinator.com> wrote in message <4979e96b-4f8b-4baa-bd00-1cd242f13c96(a)m38g2000yqd.googlegroups.com>...
> On Nov 1, 7:49?am, "Khalid " <khabu...(a)hotmail.com> wrote:
> > hi there!!
> >
> > I plotted heat contours on (x,y) plane, I wud like to know the area covered by each contour is that possible?
> > Thanks
>
> ------------------------------------------------------------------------------------------------
> How about using the polyarea() function?
From: Rob Comer on 1 Nov 2009 13:33
I'm wondering what you mean by the "area of the contour." The contours are lines, of course, so they don't have area themselves. I'm guessing that you want the area above a given contour level, or the area below that level, or the area between two adjacent levels.

You can get the patch children of the contour group from the handle h returned by contourf, and you can get the polygons defined by their XData and YData properties, but be careful -- the polyarea function is only part of the solution. What makes it challenging is that near the tops of "hills" these polygons enclose areas above a certain contour level, but near the bottoms of "pits" they enclose areas below a certain level. The inpolygon function might be useful in sorting things out.
From: Khalid on 2 Nov 2009 13:32
Thanks for your comments
Let me try to explain to you the problem, I have the X,Y,Z for a cylinder. I am calculating the radiant heat IRW which is received by this cylinder from a heating source and it is heating the cylinder from one side. I want to plot this radiant heat on the cylinder and I could do that, now I have different areas of the cylinder receiving different amount of heat. I would like to know how to calculate these areas.
Thank you again


"Rob Comer" <rob.comer.nospam(a)mathworks.com> wrote in message <hckk8u$fkn$1(a)fred.mathworks.com>...
> I'm wondering what you mean by the "area of the contour." The contours are lines, of course, so they don't have area themselves. I'm guessing that you want the area above a given contour level, or the area below that level, or the area between two adjacent levels.
>
> You can get the patch children of the contour group from the handle h returned by contourf, and you can get the polygons defined by their XData and YData properties, but be careful -- the polyarea function is only part of the solution. What makes it challenging is that near the tops of "hills" these polygons enclose areas above a certain contour level, but near the bottoms of "pits" they enclose areas below a certain level. The inpolygon function might be useful in sorting things out.
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