lesions distribution

Dear Friends,                                                         

I am a plant pathologist working in Southern Brazil. I have a research 
project dealing with the development of plant disease simulators. 
Amongst the research topics under investigation is the distribution
of disease symptoms within a particular leaf. We used a scanner to 
acquire images from wheat leaves infected with rust (a wheat disease).A 
grid x(-6,6) and y(0,100) was superimposed on each image and the number 
of lesions (z) in each cell of the grid was recorded. We have a few 
hundreds leaves examined. A example of data is shown bellow (leaf_46.txt).

x y z                                                                 

 0   0   1                                                            

 2   36  1                                                            

 1   18  1                                                            

 1   17  2                                                             

 1   32  2                                                            

 1   24  1                                                            

 1   23  1                                                            

 0   46  1                                                             

 1   43  7                                                            

 1   63  4                                                            

 -1  61  2                                                             

 1   55  2                                                            

 2   57  2                                                            

 -1  57  2                                                            

 -1  52  2                                                             

 -1  51  2                                                            

 1   51  2                                                            

 3   52  8                                                             

 0   37  2                                                            

 -1  66  6                                                            

 1   69  2                                                            

 2   72  4                                                            

 -4  73  3                                                            

 -4  72  1                                                            

 -1  70  2                                                             

 -4  67  2                                                            

 2   59  2                                                            

 -1  78  3                                                            

 0   77  1                                                            

 -2  76  2                                                            

 1   75  3                                                            

 2   27  1                                                             

 1   29  1                                                            

 0   27  1                                                            

This R code bellow was used to visualize:                                

 leaf_46 <- read.table("leaf_46.txt",header=T)                        

 win <- list(x=c(-6,-6,0,6,6), y=c(0,80,100,80,0))                    

 plot(win, asp=1, type="n")                                           

 polygon(win)                                                          

 points(leaf_46[,1:2])                                                

 

I am reading on published literature but I am still a little confused on 
choosing an appropriate technique to analyze the data. Therefore, any 
suggestions from the list members will be very welcome.

Thanks very much for your attention