CODEWITHSUNDEEP
rsubsetanova
Gautier B
Gautier B

Reputation: 11

ANOVA of subsetted data

I am manipulating a data set comprising several factors with several variables. The idea is that I want to do ANOVA analysis between factor levels nested within one level of another factor.

Here is an example similar to my data set:

     treatment category trial individual response
1          A      big     1         F1     0.10
2          A      big     2         F1     0.20
3          A      big     1         F2     0.30
4          A      big     2         F2     0.11
5          A    small     1         F3     0.12
6          A    small     2         F3     0.13
7          A    small     1         F4     0.20
8          A    small     2         F4     0.30
9          B      big     1         F5     0.40
10         B      big     2         F5     0.21
11         B      big     1         F6     0.22
12         B      big     2         F6     0.23
13         B    small     1         F7     0.31
14         B    small     2         F7     0.32
15         B    small     1         F8     0.34
16         B    small     2         F8     0.25

So basically, I'd like to do an ANOVA between big and small when treatment is A, then B, then same idea with ANOVA between big and small when treatment is A and trial 1... you get the logic.

It seems I have to use:

anova(lm(Y~x,data=dataset))

and add a subset argument, but I can't work the logic out of it and I can't find any example similar to mine. Any hint for it? Thank you in advance!

Upvotes: 1

Views: 4109

Answers (1)

João Bosco Junior
João Bosco Junior

Reputation: 55

By your description, you want to apply separated ANOVAs to different subsets of your data. Try this:

df1 <- df[df$treatment=="A",]
df2 <- df[df$treatment=="B",]
aov(response ~ category, data=df1)
aov(response ~ category, data=df2)

If you are interested in the effect of factor treatment, maybe you should keep it in a more complex model and use a posthoc to test differences within treatment A and B. But it's just a suggestion.

Upvotes: 1

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