R help - Apr 2007 - Indexing in anova summary output of the form: summary(aov(y ~ x1, Error = (x1/x2)))

Hi, there

I'm trying to get the value of the Mean Square from the ANOVA model 
summary that comes from specifying the error term, and am wondering if 
one can actually do this ( I know it's possible when using anova(lm) 
objects and the like, but I'm having a tough time with it under this 
framework). There does appear to be some indexing in the output of this 
type, but perhaps not enough to obtain single values? Here's what I've 
been able to do so far with some example code:

 > density.aov<-aov(density ~ substrate + Error(substrate/tile))
 >
 > anov1<-(summary(density.aov))
 > print(anov1)

Error: substrate
          Df Sum Sq Mean Sq
substrate  2 1282.4   641.2

Error: substrate:tile
          Df  Sum Sq Mean Sq F value Pr(>F)
Residuals 27 225.700   8.359              

Error: Within
          Df Sum Sq Mean Sq F value Pr(>F)
Residuals 60 640.00   10.67        

 > anov1[1]
$`Error: substrate`
          Df Sum Sq Mean Sq
substrate  2 1282.4   641.2

 > anov1[2]
$`Error: substrate:tile`
          Df  Sum Sq Mean Sq F value Pr(>F)
Residuals 27 225.700   8.359   

And, I can get

 > anov1[1]$Error
          Df Sum Sq Mean Sq
substrate  2 1282.4   641.2

a<-anov1[1]$Error

and then tried to get at elements in that, trying things like

a$Mean

or

a[,2]

but all return

Error:  incorrect number of dimensions

probably because

 > length(a)
[1] 1

Does anyone have any reccomendations on how to go any further here?

Cheers,

Mike

-- 
Michael D. Rennie
Ph.D. Candidate
University of Toronto at Mississauga
3359 Missisagua Rd. N. 
Mississauga, ON L5L 1C6
Ph: 905-828-5452 Fax: 905-828-3792
www.utm.utoronto.ca/~w3rennie

The output is of class "summary.anovalist" so (hint, hint) it is a
list.

Try [[ ]] to get list elements.

Without a reproducible example (see the footer and the posting guide) it 
is not possible to show you working code.


On Thu, 5 Apr 2007, Michael D. Rennie wrote:
>
> Hi, there
>
> I'm trying to get the value of the Mean Square from the ANOVA model
summary
> that comes from specifying the error term, and am wondering if one can 
> actually do this ( I know it's possible when using anova(lm) objects
and the
> like, but I'm having a tough time with it under this framework). There
does
> appear to be some indexing in the output of this type, but perhaps not
enough
> to obtain single values? Here's what I've been able to do so far
with some
> example code:
>
>> density.aov<-aov(density ~ substrate + Error(substrate/tile))
>>
>> anov1<-(summary(density.aov))
>> print(anov1)
>
> Error: substrate
>         Df Sum Sq Mean Sq
> substrate  2 1282.4   641.2
>
> Error: substrate:tile
>         Df  Sum Sq Mean Sq F value Pr(>F)
> Residuals 27 225.700   8.359 
> Error: Within
>         Df Sum Sq Mean Sq F value Pr(>F)
> Residuals 60 640.00   10.67 
>> anov1[1]
> $`Error: substrate`
>         Df Sum Sq Mean Sq
> substrate  2 1282.4   641.2
>
>> anov1[2]
> $`Error: substrate:tile`
>         Df  Sum Sq Mean Sq F value Pr(>F)
> Residuals 27 225.700   8.359 
> And, I can get
>
>> anov1[1]$Error
>         Df Sum Sq Mean Sq
> substrate  2 1282.4   641.2
>
> a<-anov1[1]$Error
>
> and then tried to get at elements in that, trying things like
>
> a$Mean
>
> or
>
> a[,2]
>
> but all return
>
> Error:  incorrect number of dimensions
>
> probably because
>
>> length(a)
> [1] 1
>
> Does anyone have any reccomendations on how to go any further here?
>
> Cheers,
>
> Mike
>
>
-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595