R-users:

My problem: the package fdim (which measures fractal dimensions of  
datasets) apparently prefers 3-D (XYZ) datasets.  I'm trying to  
measure the information dimension (a type of fractal dimension) of a  
2-D (XY) dataset.

Here's some examples of the preferred 3-D data (XYZ):

library(fdim)
XYZ <- (makehplane(NumN=300, DimM=3, Longit=300))
fdim(XYZ,q=0.999999,PlotF=TRUE)

Here's an example of the type of data I have:

library(fdim)
X<- sample(1:1000,size=300,replace=TRUE)
Y<- sample(1:500,size=300,replace=TRUE)
XY<- matrix(c(X,Y),nrow=300)
fdim(XY,q=0.999999,PlotF=TRUE)

My question is this: since fdim prefers XYZ data, is it invalid to  
use fdim to measure the fractal dimension of XY data?  What I have is  
XY position data of individual trees in a section of forest.  I'd  
like to measure the information dimension of the distribution of trees.

The reason I'm asking my question is that fdim returns consistently  
higher dimension numbers than do other fractal-measuring programs.   
However, those other programs measure the fractal dimension of  
bitmaps, not datasets, and have a problem with resolution--many of  
the points on the bitmap overlap, making it impossible to measure the  
dimension of those points.  Therefore, I'd like to measure the  
information dimension using a program that uses datasets, not bitmaps.

Thanks for your input.

Jim Milks
Graduate Student
Environmental Sciences Ph.D. Program
Wright State University
Dayton, OH 45435

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