[R] How to get the n (number of observations) per conditional group

[Erik Iverson]

We will only be able to help if you provide a reproducible example!  I'm sure this is a simple one-liner, but it's hard to tell from your example what it should be.  The functions table, length, tapply, and/or nrow may play a part though. 

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of Dax
Sent: Thursday, August 13, 2009 9:11 AM
To: r-help at r-project.org
Subject: [R] How to get the n (number of observations) per conditional group

Hello all,

I have a huge data set that I'm cleaning up a bit. I am extracted the
means per condition, but also need to get the n. Strangely enough I am
unable to find a function that could actually pull this off. I am
unable to use replications or count the rows using nrow.

What I am trying to obtain is the number of observations fitting
something along the lines of "data$total[data$spp==1&data$gyro==1&data
$salinity==0&data$day==i]"

Can anyone help me?

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