Kevin,

I guess this may not have a one line solution (I may be wrong). I would try
something like this:
-Get all the unique (use 'unique') values in 'temp'
-Loop through these values and extract the subset of data and perform the
ANOVA on this subset.

As an example, code may go something like this:

X<-data.frame(temp=c(12,12,12,12,12,14,14,12,14,14,14,14),
 day=c('LD','LD','SD','LD','SD','SD','LD','SD','LD','LD','SD','SD'),
 var=rnorm(12))

temp_unique <- unique(X$temp)
for (i in seq(temp_unique)){
  Y <- X[X$temp==temp_unique[i],]
  # perform ANOVA here on Y
}

You may have to append the ANOVA results to another variable to retrieve
them.

Do the same for 'line' too.

-Ashoka.
---
Scientist
Pacific Northwest National Laboratory
Richland, WA


On Dec 13, 2007 12:21 PM, Kevin J Emerson <[EMAIL PROTECTED]> wrote:

> Hello R help-ers,
>
>
> I have a basic question, but I have been playing with it for a while and
> haven't quite gotten a hang of how to get it working.  I want to perform
> multiple one-way ANOVAs on subsets of data and am not sure how to do it in
> an automated way.  I am thinking of doing something similar to 'aggregate'
> but I would like to collect all of the ANOVA results in a way in which I
> can
> get to the information from each of the independent ANOVAs.  In effect, I
> would like a data frame with each of the subset identifiers, F and P
> values
> in the rows.  Or a list of all of the ANOVA summaries or something like
> that.
>
>
>
> I would like to do an anova of the form aov(var ~ day) for each subset of
> data corresponding to "temp" and "line".  I have lots of temps and lines
> and
> would like to do this in an automated fashion.  I know of the aggregate
> function for doing this kind of thing to compute means etc, but I am not
> sure how to call an anova in this way.  I have looked at "by" and "apply"
> and have tried various things but am unable to get it to work.
>
>
>
> Any help  would be greatly appreciated.  A sample of the dataset is below.
>
>
>
> Thank you for your time,
>
> Kevin
>
>
>
>
>
>   temp  line       day                 var
>
>     12 WMG 1        LD               70.59
>
>     12 WMG 1        LD              100.00
>
>     12 WMG 1        LD              100.00
>
>     12 WMG 1        SD               85.00
>
>     12 WMG 1        SD               75.00
>
>     12 WMG 1        SD               90.00
>
>     12 WMG 2        LD              100.00
>
>     12 WMG 2        LD               83.33
>
>     12 WMG 2        LD              100.00
>
>     12 WMG 2        SD               91.67
>
>     14 WMG 1        LD               76.03
>
> .
>
>
>
>
>
>
>
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> 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.
>



-- 
---
Scientist
Pacific Northwest National Laboratory
Richland, WA

        [[alternative HTML version deleted]]

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