[R] Learning ANOVA

[Stephen Liu]

Hi JesperHybel,

Thanks for your advice.

>If you're trying to follow the youtube video you have a typing mistake here:

>InsectSprays.aov <-(test01$count ~ test01$spray)

>I think this should be:

>InsectSprays.aov <-aov(test01$count ~ test01$spray)


Your advice works for me.  Sorry I missed "aov" before(test01$count ~ 
test01$spray)

> InsectSprays.aov <- aov(test01$count ~ test01$spray)
> summary(InsectSprays.aov)
             Df Sum Sq Mean Sq F value    Pr(>F)    
test01$spray  5 2668.8  533.77  34.702 < 2.2e-16 ***
Residuals    66 1015.2   15.38                      
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 


> TukeyHSD(InsectSprays.aov)
  Tukey multiple comparisons of means
    95% family-wise confidence level

Fit: aov(formula = test01$count ~ test01$spray)

$`test01$spray`
           diff        lwr       upr     p adj
B-A   0.8333333  -3.866075  5.532742 0.9951810
C-A -12.4166667 -17.116075 -7.717258 0.0000000
D-A  -9.5833333 -14.282742 -4.883925 0.0000014
E-A -11.0000000 -15.699409 -6.300591 0.0000000
F-A   2.1666667  -2.532742  6.866075 0.7542147
C-B -13.2500000 -17.949409 -8.550591 0.0000000
D-B -10.4166667 -15.116075 -5.717258 0.0000002
E-B -11.8333333 -16.532742 -7.133925 0.0000000
F-B   1.3333333  -3.366075  6.032742 0.9603075
D-C   2.8333333  -1.866075  7.532742 0.4920707
E-C   1.4166667  -3.282742  6.116075 0.9488669
F-C  14.5833333   9.883925 19.282742 0.0000000
E-D  -1.4166667  -6.116075  3.282742 0.9488669
F-D  11.7500000   7.050591 16.449409 0.0000000
F-E  13.1666667   8.467258 17.866075 0.0000000


I made a comparison of my result with "example(InsectSprays).  They looks the 
same.

I also compared "plot(InsectSprays.aov)".


A further question how to plot 4 graphs simultaneously?  Instead of reading 
them, individually.  I read ?plot but unable to resolve.

Also how to save InsectSprays.aov?  I think I can only save it as 
InsectSprays.csv.  I can't find "write.aov" command. 


Thanks


TIA

B.R.
satimis






----- Original Message ----
From: JesperHybel <jesperhybel at hotmail.com>
To: r-help at r-project.org
Sent: Sat, August 14, 2010 2:09:48 AM
Subject: Re: [R] Learning ANOVA


If you're trying to follow the youtube video you have a typing mistake here:

InsectSprays.aov <-(test01$count ~ test01$spray)

I think this should be:

InsectSprays.aov <-aov(test01$count ~ test01$spray)


youre missing the functioncall "aov" on the right hand side of the
assignment operator '<-'.

the results of the application of function aov() is stored in
InsectSprays.aov and is accessed through

summary(InsectSprays.aov)

since you missed the functioncall you cannot apply TukeyHSD() to
InsectSprays.aov

I think
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