Hello everybody, I would like to solve the problem described below in R (if possible). I am very new to R and have therefore no idea what to even look for in the docu. Therefore, if someone could tell me if this is possible in R and where I might find the respective docu then I would already be very thankful. I have a large set (a few million) of points in 3D. I would like to create a contour density plot that would show a surface of constant density which includes e.g. 50% of the points. Ideally, the surface would be semitransparent, such that I can show two or three at the same time. Alternatively, if I would calculate the contour surfaces myself, could I use R to semitransparently visualize a triangulated surface? Thank you very much for your help Lutz
3D density plot of point set
3 messages · Lutz Gehlen, Duncan Murdoch
On 13/07/2011 3:56 AM, Lutz Gehlen wrote:
Hello everybody, I would like to solve the problem described below in R (if possible). I am very new to R and have therefore no idea what to even look for in the docu. Therefore, if someone could tell me if this is possible in R and where I might find the respective docu then I would already be very thankful. I have a large set (a few million) of points in 3D. I would like to create a contour density plot that would show a surface of constant density which includes e.g. 50% of the points. Ideally, the surface would be semitransparent, such that I can show two or three at the same time. Alternatively, if I would calculate the contour surfaces myself, could I use R to semitransparently visualize a triangulated surface?
For the latter, see the misc3d package, in particular the contour3d function. Use the rgl engine with alpha=0.5 (or some other value) for semi-transparency. For computing the density estimates there are lots of choices, including the kde3d function that's also in the misc3d package. To find the contour holding 50% of the points, compute the density at all of them, and find the median density. Duncan Murdoch
Hello Duncan, thank you for your reply. I will have a look at the misc3d package and at contour3d and kde3d in particular. Cheers, Lutz