[R] Tukey tests in two-way ANOVA

[peter dalgaard]

I think you forgot to turn site and year into factors. (The 1 Df is the giveaway).

-pd

> On 15 May 2017, at 19:40 , Lucy McMahon <lucymcmahon004 at hotmail.co.uk> wrote:
> 
> R-help:
> 
> I'm looking into the abundance of an algal species over site and years using a two-way ANOVA:
> 
>> summary (aov (fserratus ~ site+year))
>            Df     Sum Sq   Mean Sq   F value      Pr(>F)
> site       1      1487       1486.6      6.094       0.0155 *
> year      1      1173      1172.8      4.808       0.0309 *
> 
> But I'm receiving the following warning messages when I run the Tukey test.
>> TukeyHSD(aov(fserratus ~ site+year))
> 
> $site
>                    diff              lwr                      upr                 p adj
> 1-0         -8.039565     -14.51045     -1.568685    0.0154723
> 
> Warning messages:
> 1: In replications(paste("~", xx), data = mf) : non-factors ignored: year
> 2: In TukeyHSD.aov(aov(fserratus ~ site + year)) :
>  'which' specified some non-factors which will be dropped
> 
> 
> Any advice would be appreciated, thanks.
> 
> 
> 
> 
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> 
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-- 
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
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