R help - Mar 2010 - black cluster in salt and pepper image

Hi,

on a lattice, I have binary 0/1 data. 1s are rare and may form clusters. 
I would like
to know the size/length of largest cluster. Any help warmly welcome,

Sylvain.

Hello,

The function bwlabel() in the Bioconductor package EBImage, extracts the 
connected components of an image. Denoting your binary matrix by x, the 
following code gives you the first 10 largest clusters (in size).

 > library(EBImage)
 > y = bwlabel(x)
 > sort(table(y), dec=TRUE)[1:10]

See http://www.bioconductor.org/packages/release/bioc/html/EBImage.html 
how to download/install EBImage.

Best regards,

Greg
---
Gregoire Pau
EMBL Research Officer
http://www.ebi.ac.uk/~gpau/


Sylvain Sardy wrote:
> Hi,
> 
> on a lattice, I have binary 0/1 data. 1s are rare and may form clusters. 
> I would like
> to know the size/length of largest cluster. Any help warmly welcome,
> 
> Sylvain.
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

You might also want to look at the ImageJ application,

http://rsb.info.nih.gov/ij/

which IIRC has a bunch of tools designed to pick out clusters, dots, etc.


Carl