[R] unbalanced effects in aov

Brooke LaFlamme bal44 at cornell.edu
Fri Sep 14 21:18:34 CEST 2007


Hi, I have been having some trouble using aov to do an anova, probably because I'm not understanding how to use this function correctly. For some reason it always tells me that "Estimated effects may be unbalanced", though I'm not sure what this means. Is the formula I am using written incorrectly? Below is the code I am using along with the data: 

> my.data
         response species sex line replicate plate
1   -7.092854e-03       1   1    1         1     1
2   -8.663481e-04       1   2    1         1     1
3   -5.797276e-03       1   1    2         1     1
4   -2.598078e-03       1   2    2         1     1
5    7.832551e-04       2   1    1         1     1
6    1.333361e-03       2   2    1         1     1
7   -8.972490e-04       2   1    2         1     1
8   -2.834589e-03       2   2    2         1     1
9    5.655464e-04       3   1    1         1     1
10   7.371403e-03       3   2    1         1     1
11   3.160040e-03       3   1    2         1     1
12  -4.110653e-03       1   1    2         2     2
13  -2.262314e-03       1   2    2         2     2
14  -3.259483e-03       1   1    3         1     2
15  -5.671712e-03       1   2    3         1     2
16  -3.636077e-03       2   1    2         2     2
17  -3.904864e-03       2   2    2         2     2
18   1.025440e-03       2   1    3         1     2
19  -3.789292e-03       2   2    3         1     2
20   3.396270e-03       3   1    2         2     2
21   8.807778e-03       3   2    2         2     2
22   5.456604e-03       3   2    3         1     2
23  -1.134216e-02       1   1    3         2     3
24  -7.725740e-03       1   2    3         2     3
25  -1.589719e-03       1   1    4         1     3
26   4.574659e-04       1   2    4         1     3
27  -2.899983e-03       2   1    3         2     3
28  -4.310185e-03       2   2    3         2     3
29  -3.200475e-05       2   1    4         1     3
30   3.166308e-03       3   1    3         2     3
31   5.697712e-03       3   2    3         2     3
32   6.058486e-03       3   1    4         1     3
33   6.941016e-03       3   2    4         1     3
34  -2.794982e-03       1   1    4         2     4
35  -4.416711e-03       1   1    5         1     4
36  -4.062832e-03       1   2    5         1     4
37   1.763941e-03       2   1    4         2     4
38  -2.928930e-03       2   2    4         2     4
39  -2.869975e-03       2   2    5         1     4
40   6.949621e-03       3   1    4         2     4
41   5.766447e-03       3   2    4         2     4
42   2.510278e-03       3   1    5         1     4
43   5.507496e-03       3   2    5         1     4
44  -1.197325e-02       1   2    5         2     5
45  -6.556955e-03       1   1    6         1     5
46   3.622169e-04       2   1    5         2     5
47  -1.288784e-03       2   2    5         2     5
48  -2.863541e-03       2   1    6         1     5
49  -7.082933e-03       2   2    6         1     5
50   3.813700e-03       3   1    5         2     5
51   9.593295e-03       3   2    5         2     5
52   9.881930e-03       3   2    6         1     5
53  -1.081725e-02       1   1    6         2     6
54  -8.870041e-03       1   2    6         2     6
55  -5.305931e-04       1   2    7         1     6
56   2.835570e-03       2   1    6         2     6
57   4.541555e-03       2   2    6         2     6
58  -5.909101e-03       2   1    7         1     6
59  -2.768342e-03       2   2    7         1     6
60   8.835976e-03       3   1    6         2     6
61   1.234038e-02       3   2    6         2     6
62   2.015527e-03       3   1    7         1     6
63   6.485565e-03       3   2    7         1     6
64  -8.372922e-03       1   1    7         2     7
65  -9.439749e-03       1   2    7         2     7
66  -3.782672e-03       1   1    8         1     7
67  -2.576470e-03       1   2    8         1     7
68   2.878789e-03       2   1    7         2     7
69  -9.458139e-04       2   2    7         2     7
70  -3.993852e-03       2   2    8         1     7
71   5.997718e-03       3   1    7         2     7
72  -9.595505e-05       3   1    8         1     7
73   8.167411e-03       3   2    8         1     7
74  -1.181158e-02       1   1    8         2     8
75  -1.072585e-02       1   2    8         2     8
76  -2.856532e-03       1   1    9         1     8
77  -4.944013e-03       1   2    9         1     8
78   2.558783e-03       2   1    8         2     8
79   3.393314e-03       2   2    8         2     8
80  -4.466758e-03       2   1    9         1     8
81  -5.667622e-03       2   2    9         1     8
82   7.491253e-03       3   2    8         2     8
83   4.380724e-03       3   1    9         1     8
84   2.827233e-03       3   2    9         1     8
85  -7.433928e-03       1   2    9         2     9
86  -9.177664e-03       1   1   10         1     9
87  -6.040020e-04       1   2   10         1     9
88   1.394224e-03       2   1    9         2     9
89  -7.455449e-04       2   1   10         1     9
90  -2.251806e-03       2   2   10         1     9
91   7.865773e-03       3   1    9         2     9
92   6.287781e-03       3   2    9         2     9
93   7.734405e-03       3   1   10         1     9
94   9.757342e-03       3   2   10         1     9
95  -6.876948e-03       1   1    1         2    10
96  -4.974144e-03       1   2    1         2    10
97  -2.959226e-03       1   1   10         2    10
98   8.058296e-04       1   2   10         2    10
99   5.314729e-03       2   1    1         2    10
100  1.251126e-03       2   2    1         2    10
101  4.012311e-03       2   2   10         2    10
102  3.479155e-03       3   1    1         2    10
103  1.144813e-02       3   2    1         2    10
104  4.090214e-03       3   1   10         2    10
105  5.196910e-03       3   2   10         2    10
106 -9.038264e-03       1   2    6         1    11
107 -6.184877e-03       1   1    7         1    11
108  4.255164e-03       2   2    4         1    11
109  8.291281e-03       2   1    5         1    11
110 -5.368315e-04       2   2    9         2    11
111 -7.792906e-04       2   1   10         2    11
112  6.312335e-03       3   1    3         1    11
113  1.243561e-02       3   2    7         2    11
114  6.223999e-04       3   1    8         2    11
115 -6.517484e-03       1   2    4         2    12
116 -1.009622e-02       1   1    5         2    12
117 -4.414381e-04       1   1    9         2    12
118  2.221470e-03       2   1    8         1    12
119  1.041818e-02       3   2    2         1    12
120  3.384938e-04       3   1    6         1    12

I am treating all the variables as factors (except for response, obviously). 

formula<-response~species+line%in%species+replicate%in%line+sex%in%species+plate
model<-aov(formula, data=my.data)

This is the output: 

> model
Call:
   aov(formula = formula, data = my.data)

Terms:
                     species        plate species:line line:replicate
Sum of Squares  0.0026469288 0.0000945202 0.0003320255   0.0002008000
Deg. of Freedom            2           11           27             10
                 species:sex    Residuals
Sum of Squares  0.0001383116 0.0006315465
Deg. of Freedom            3           66

Residual standard error: 0.003093362 
Estimated effects may be unbalanced

Any help would be greatly appreciated as the R help documentation for aov does not address this issue. 

Thanks!
--
Brooke LaFlamme



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