Jason Hwa wrote:
Dear R-help community,
I am working with multidimensional contingency tables and I am having
trouble getting loglm to run on all dimensions without typing out each
dimension.
I have generated random data and provided output for the results I want
below:
d1.c1 <- rnorm(20, .10, .02)
d1.c2 <- rnorm(20, .10, .02)
d2.c1 <- rnorm(20, .09, .02)
d2.c2 <- rnorm(20, .09, .02)
d3.c1 <- rnorm(20, .11, .02)
d3.c2 <- rnorm(20, .11, .02)
group1 <- cbind(1, d1.c1, d2.c1, d3.c1)
group2 <- cbind(2, d1.c2, d2.c2, d3.c2)
colnames(group1) <- colnames(group2) <- c("group", "dim1", "dim2", "dim3")
combined <- rbind(group1, group2)
combined[,2:4] <- combined[,2:4] > .1
ctables <- xtabs(~., data = combined)
loglm(~group+dim1+dim2+dim3, data=ctables)
Call:
loglm(formula = ~group + dim1 + dim2 + dim3, data = ctables)
Statistics:
X^2 df P(> X^2)
Likelihood Ratio 12.29856 11 0.3416253
Pearson 10.28058 11 0.5053391
However, the number and the names of the dimensions change for each
dataset. What I want is to be able to run the following line at the end
of the code: "loglm(~., data=ctables)", but it always prints the
following error:
Error in terms.formula(formula <- denumerate(formula)) :
'.' in formula and no 'data' argument
Can anyone help me out?
Thank you,
Jason
Presumably you're using loglm from package MASS (which you
should indicate).
To use the dot notation, you need to put your data in
dataframe form. This works:
d <- data.frame(ftable(ctables))
loglm(Freq ~ ., data = d)
Or you could use the integer notation for the formula:
loglm( ~ 1 + 2 + 3 + 4, data = ctables)
You could generate the formula in your code:
form <- as.formula(paste("~", paste(1:4, collapse="+")))
and then use
loglm(form, data = ctables)
-Peter Ehlers
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