Alexy Khrabrov wrote: >I get tables with millions of rows. For plotting to a screen-size >jpg, obviously just about 1000 points are enough. Instead of feeding >plot() the original millions of rows, I'd rather shrink the original >dataframe, using some kind of the following interpolation: > >-- split dataframe into chunks of N rows each, e.g. 1000 rows each >-- compute average for each column >-- issue one new row of those averages into the shrunk result > >Is there any existing package to do that in R? Otherwise, which R >idioms are most effective to achieve that? > >Cheers, >Alexy > > > > Hi,
if you want to extract relevant information from such a table, splitting rows in arbitrary chuncks may not solve your problem. Ordinations in reduced space are designed for that kind of task, but hierachical clustering may also help. See Legendre & Legendre (1998, Numerical Ecology, Elsevier) for examples of such methods in Ecology, and the R packages ade4, vegan and hclust. Regards, Thibaut. -- ###################################### Thibaut JOMBART CNRS UMR 5558 - Laboratoire de Biométrie et Biologie Evolutive Universite Lyon 1 43 bd du 11 novembre 1918 69622 Villeurbanne Cedex Tél. : 04.72.43.29.35 Fax : 04.72.43.13.88 [EMAIL PROTECTED] http://lbbe.univ-lyon1.fr/-Jombart-Thibaut-.html?lang=en http://pbil.univ-lyon1.fr/software/adegenet/ ______________________________________________ R-help@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.
