[R] how to read the "Sum Sq" - column from summary.aov()

[Peter Ehlers]

On 2011-02-03 04:30, Bertolt Meyer wrote:
> Dear R-Users,
>
> I have a trivial problem, but extensive googling and ??'ing did not solve it: I want to obtain the sums of squares from a summary.aov() object for later use. Example:
>
>> DV<- rnorm(100)
>> IV1<- as.factor(rep(c("male", "female"), times = 50))
>> IV2<- as.factor(rep(c("young", "old"), times = 50))
>>
>> summary(aov(DV ~ IV1 * IV2))
>
>              Df Sum Sq Mean Sq F value Pr(>F)
> IV1          1  0.215 0.21499  0.2277 0.6343
> Residuals   98 92.523 0.94411
>
> How can I store the sums of squares in a variable for later use? Like this:
>
>> some.magic.command()
> [1]  0.215  92.523

str() is your friend.

  str( summary(aov(DV ~ IV1 * IV2)) )

shows that the summary is a list containing a data.frame.
Use

  summary(aov(DV ~ IV1 * IV2))[[1]]

to extract the data.frame and any one of

  summary(aov(DV ~ IV1 * IV2))[[1]][, 2]
  summary(aov(DV ~ IV1 * IV2))[[1]][, 'Sum Sq']
  summary(aov(DV ~ IV1 * IV2))[[1]]$'Sum Sq'

to extract the sum-of-squares vector.

Peter Ehlers

>
> Thank you,
> Bertolt
>