[R] working with summarized data

From: Rick Bischoff <rdbisch_at_gmail.com>
Date: Thu 31 Aug 2006 - 00:27:58 EST

The data sets I am working with all have a weight variable--e.g., each row doesn't mean 1 observation.

With that in mind, nearly all of the graphs and summary statistics are incorrect for my data, because they don't take into account the weight.

For example "median" is incorrect, as the quantiles aren't calculated with weights:

sum( weights[X < median(X)] ) / sum(weights)

This should be 0.5... of course it's not.

Unfortunately, it seems that most(all?) of R's graphics and summary statistic functions don't take a weight or frequency argument. (Fortunately the models do...)

Am I completely missing how to do this? One way would be to replicate each row proportional to the weight (e.g. if the weight was 4, we would 3 additional copies) but this will get prohibitive pretty quickly as the dataset grows.

Thanks in advance!

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