Try this:

sapply(sapply(summary(bgaov), '[[', 1), '[[', 'Mean Sq')

On Mon, Sep 14, 2009 at 4:45 PM, Paul <paul@paulhurley.co.uk> wrote:

> I'm trying to write a function to automate doing a variance analysis, part
> of which involves doing some further calculations. The method I've been
> using isn't very robust, if variable names change then it stops working.
>
> For this dummy data
>
> > dput(assayvar,"")
> structure(list(Run = structure(c(1L, 1L, 1L, 2L, 2L, 2L, 3L,
> 3L, 3L, 4L, 4L, 4L), .rk.invalid.fields = list(), .Label = c("1",
> "2", "3", "4"), class = "factor"), Actual = c(246.3, 253.6, 247.6,
> 249, 249, 251.3, 254.9, 254.1, 253.2, 250, 248.9, 250.3)), .Names =
> c("Run",
> "Actual"), row.names = c(NA, 12L), class = "data.frame")
>
> > assayaov<-aov(Actual~Run+Error(Run),data=assayvar)
> > str(summary(assayaov))
> List of 2
> $ Error: Run :List of 1
> ..$ :Classes ‘anova’ and 'data.frame': 1 obs. of 3 variables:
> .. ..$ Df : num 3
> .. ..$ Sum Sq : num 46.5
> .. ..$ Mean Sq: num 15.5
> ..- attr(*, "class")= chr [1:2] "summary.aov" "listof"
> $ Error: Within:List of 1
> ..$ :Classes ‘anova’ and 'data.frame': 1 obs. of 5 variables:
> .. ..$ Df : num 8
> .. ..$ Sum Sq : num 36.4
> .. ..$ Mean Sq: num 4.55
> .. ..$ F value: num NA
> .. ..$ Pr(>F) : num NA
> ..- attr(*, "class")= chr [1:2] "summary.aov" "listof"
> - attr(*, "class")= chr "summary.aovlist"
>
> But for this dummy data
>
> > dput(BGBottles,"")
> structure(list(Machine = structure(c(1L, 1L, 1L, 2L, 2L, 2L,
> 3L, 3L, 3L, 4L, 4L, 4L), .rk.invalid.fields = structure(list(), .Names =
> character(0)), .Label = c("1",
> "2", "3", "4"), class = "factor"), Weight = c(14.23, 14.96, 14.85,
> 16.46, 16.74, 15.94, 14.98, 14.88, 14.87, 15.94, 16.07, 14.91
> )), .Names = c("Machine", "Weight"), row.names = c(NA, 12L), class =
> "data.frame")
>
> > bgaov<-aov(Weight~Machine+Error(Machine),data=BGBottles)
> > str(summary(bgaov))
> List of 2
> $ Error: Machine:List of 1
> ..$ :Classes ‘anova’ and 'data.frame': 1 obs. of 3 variables:
> .. ..$ Df : num 3
> .. ..$ Sum Sq : num 5.33
> .. ..$ Mean Sq: num 1.78
> ..- attr(*, "class")= chr [1:2] "summary.aov" "listof"
> $ Error: Within :List of 1
> ..$ :Classes ‘anova’ and 'data.frame': 1 obs. of 5 variables:
> .. ..$ Df : num 8
> .. ..$ Sum Sq : num 1.45
> .. ..$ Mean Sq: num 0.182
> .. ..$ F value: num NA
> .. ..$ Pr(>F) : num NA
> ..- attr(*, "class")= chr [1:2] "summary.aov" "listof"
> - attr(*, "class")= chr "summary.aovlist"
>
> So the code to get the mean square value
>
> machine<-summary(bgaov)$"Error: Machine"[[1]]$"Mean Sq"
>
> Doesn't work, because the Machine but won't always be Machine.
>
> Any better way to do this ?
>
> Thanks
>
> Paul.
>
> ______________________________________________
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> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O

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