[R] Automatically Extracting F- and P- vals from ANOVA
John Fox
jfox at mcmaster.ca
Mon Jan 31 23:26:52 CET 2005
Dear Uri,
You can save the object produced by summary() (i.e., assign it to a
variable, not print it and dump it to a file) and extract what you want from
that. You can use str() to see the structure of the object.
I hope this helps,
John
--------------------------------
John Fox
Department of Sociology
McMaster University
Hamilton, Ontario
Canada L8S 4M4
905-525-9140x23604
http://socserv.mcmaster.ca/jfox
--------------------------------
> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Uri
> Sent: Monday, January 31, 2005 4:07 PM
> To: r-help at stat.math.ethz.ch
> Subject: [R] Automatically Extracting F- and P- vals from ANOVA
>
> Dear R community,
>
> I'm currently using R to analyze functional Magnetic
> Resonance Imaging data. Each analysis involves running
> ~120,000 repeated-measures ANOVAs.
>
> I would like to know if there is any automatic way to access
> the F- and P-value data that are associated with each of
> these 120,000 ANOVAs.
>
> For example, if the summary output (for the 1st ANOVA of
> 120,000) shows the following value for factor "C", then I
> would like to automatically extract the F value (4.1) and P
> value (0.13) from the
> summary() output:
>
> > summary(anova.1)
>
> Error: S
> Df Sum Sq Mean Sq F value Pr(>F)
> Residuals 1 12.5 12.5
>
> Error: S:C
> Df Sum Sq Mean Sq F value Pr(>F)
> C 3 128.500 42.833 4.2131 0.1341
> Residuals 3 30.500 10.167
>
> Of course, I would be interested only in factor "C".
>
> I would then push these values to a hash of hashes (i.e, multi-dim
> array) that summarizes the results of all the ANOVAs.
> {Anova1, (F=4.21), (P=0.13)} etc'.
>
> I "dumped" a sample aov object, and my impression was that
> the F and P values for each effect are not hard coded, but
> constructed on the fly by the summary() function.
>
> Is there a script or function that already does what I am looking for?
> If not, my second option would be to sink the summary of
> each anova to a text file, and then post-process it, but this
> latter option is sub-optimal.
>
> Best,
> Uri Hasson
>
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