How can I make a trace or curve around a set of points to signify region?

Hi everyone,

 So I have a figure that contains 3 sets of data. For each of the sets of data, there are points that cluttered in a certain region of the 3D plot. I was wondering how I could possibly trace or put a curve *around* the points. So in theory I want to include just a *region* where the points were found and not the points themselves. Thank you in advance for your help.

Casey

Answer 1

[Matt J]

You could use IMFREEHAND or IMPOLY if you have the Image Processing Toolbox.

[Casey]

I'm a little naive on the Image Processing Toolbox, how could I check to see if I have it?

[Matt J]

One way is to try the commands. If you don't have the toolbox, the commands won't work ;)

You can also use the VER command to get a list of all your toolboxes.

Answer 2

[Image Analyst]

MATLAB does not have ways to "carve out" some irregular region in 3D space - not that I'm aware of anyway. I would certainly be using it for color segmentation if they had something.

Your best bet is to make projections along the 3 directions and use something like imfreehand(), imrect(), rbbox(), roipoly(), or roipolyold() to outline regions in each of the three projections. From there, you could just use those, or you could build a 3D lookup table (3D mask).

[Matt J]

You could also possibly use these FEX files to draw the convex polyhedral hull of the groups of points

http://www.mathworks.com/matlabcentral/fileexchange/9261-plot-2d3d-region

http://www.mathworks.com/matlabcentral/fileexchange/30892-representing-polyhedral-convex-hulls-by-vertices-or-inequalities