R help - Aug 2009 - 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?

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?

______________________________________________
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.

?length

--- On Thu, 8/13/09, Dax <rienk.doetjes at gmail.com> wrote:
> From: Dax <rienk.doetjes at gmail.com>
> Subject: [R] How to get the n (number of observations) per conditional
group
> To: r-help at r-project.org
> Received: Thursday, August 13, 2009, 10:11 AM
> 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?
> 
> ______________________________________________
> 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.
> 

      __________________________________________________________________
[[elided Yahoo spam]]

I found a work-around by just simply getting the sum of the
conditional values and dividing this by the mean. It's not elegant but
it works

On Aug 13, 3:11?pm, Dax <rienk.doet... at gmail.com>
wrote:
> 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?
>
> ______________________________________________
> R-h... at r-project.org mailing
listhttps://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guidehttp://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.