# [R] Error: object is not a matrix

Albert Kim alkim at u.washington.edu
Thu Aug 22 20:39:12 CEST 2002

```Hi,

I have encountered the following error, when using 'aov', which I think
has something to do with the length of my call to 'aov', and I cannot
understand why:

Error in model.frame.default(formula = Y2 ~ P2 + P2:AAAAAAAA +
P2:B2 +  :
object is not a matrix

The error occurs when I run the first sequence below, but not the
second.  The two sequences are based on the SAME data, but in one
case, the variable names are longer [Although I don't think the nature
of my analysis is relevant here, it is a 3-way repeated measures
ANOVA;  the "P" factor is a random factor for participants in an
experiment and the A,B,C factors are factorially crossed within P].

## RESULTS IN ERROR:
> AK2.df <<- read.table("foo.data", col.names = c("Y2",
"P2","AAAAAAAA","B2","C2"))
> AK2.df\$P2 <- as.factor(AK2.df\$P2)
> attach(AK2.df)
> AK2anova.out <- aov(Y2 ~ AAAAAAAA * B2 * C2 + Error(P2 + P2:AAAAAAAA +
P2:B2 + P2:C2 + P2:AAAAAAAA:B2 + P2:AAAAAAAA:C2 + P2:B2:C2 +
P2:AAAAAAAA:B2:C2), data=AK2.df)

Error in model.frame.default(formula = Y2 ~ P2 + P2:AAAAAAAA + P2:B2 +  :
object is not a matrix

## IDENTICAL ANALYSIS WITH DIFFERENT VARIABLE NAMES DOES NOT PRODOCE
ERROR:
> AK.df <<- read.table("foo.data", col.names = c("Y", "P","A","B","C"))
> AK.df\$P <- as.factor(AK.df\$P)
> attach(AK.df)
> AKanova.out <- aov(Y ~ A * B * C + Error(P + P:A + P:B + P:C + P:A:B +
P:A:C + P:B:C + P:A:B:C), data=AK.df)

I have reproduced this error in a number of ways, and the only common
characteristic I can see to my actions is that the length of the call
to 'aov' is always too long:  either one of the variable names is too
long, or I include too many error terms, etc...).

Any help would be appreciated,
Al Kim
Research Scientist
Department of Psychology
University of Washington, Box 351525
Seattle, WA. 98195, USA
E-Mail:  alkim at u.washington.edu;  Tel: (206)543-2395

Included below is the data I'm using.

> AK.df
Y P  A     B       C
1  10 1 E1   Red   Agent
2   9 1 E1   Red Patient
3   0 1 E1 Unred   Agent
4   0 1 E1 Unred Patient
5   5 1 E2   Red   Agent
6   6 1 E2   Red Patient
7   0 1 E2 Unred   Agent
8   0 1 E2 Unred Patient
9   8 2 E1   Red   Agent
10  9 2 E1   Red Patient
11  0 2 E1 Unred   Agent
12  0 2 E1 Unred Patient
13  4 2 E2   Red   Agent
14  4 2 E2   Red Patient
15  0 2 E2 Unred   Agent
16  0 2 E2 Unred Patient
17 12 3 E1   Red   Agent
18 11 3 E1   Red Patient
19  2 3 E1 Unred   Agent
20  0 3 E1 Unred Patient
21  6 3 E2   Red   Agent
22  7 3 E2   Red Patient
23  0 3 E2 Unred   Agent
24  0 3 E2 Unred Patient

> AK2.df
Y2 P2 AAAAAAAA    B2      C2
1  10  1       E1   Red   Agent
2   9  1       E1   Red Patient
3   0  1       E1 Unred   Agent
4   0  1       E1 Unred Patient
5   5  1       E2   Red   Agent
6   6  1       E2   Red Patient
7   0  1       E2 Unred   Agent
8   0  1       E2 Unred Patient
9   8  2       E1   Red   Agent
10  9  2       E1   Red Patient
11  0  2       E1 Unred   Agent
12  0  2       E1 Unred Patient
13  4  2       E2   Red   Agent
14  4  2       E2   Red Patient
15  0  2       E2 Unred   Agent
16  0  2       E2 Unred Patient
17 12  3       E1   Red   Agent
18 11  3       E1   Red Patient
19  2  3       E1 Unred   Agent
20  0  3       E1 Unred Patient
21  6  3       E2   Red   Agent
22  7  3       E2   Red Patient
23  0  3       E2 Unred   Agent
24  0  3       E2 Unred Patient

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