I've been having a problem using the step function to evaluate models. I've
simplified the code and get the same problem using the dataset Titanic. The
relevant code and output is below. The problem disappears (i.e., 'step' runs
correctly) if I rerun the code but change the 'loglm' call to explicitly
reference Titanic instead of X (as in: loglm(as.formula(Y),data=Titanic)).
What is causing this?
TIA,
DAV
----------
> catn<-function(...) cat(...,"\n")
> local({ X<-Titanic; print(class(X));
Y<-paste('~',paste(names(dimnames(X)),collapse="*"));
print(Y);
sm<-loglm(as.formula(Y),data=X);
catn("SM"); print(sm); catn('running');
step(sm,direction='backward') })
Output:
[1] "table"
[1] "~ Class*Sex*Age*Survived"
SM
Call:
loglm(formula = as.formula(Y), data = X)
Statistics:
X^2 df P(> X^2)
Likelihood Ratio 0 0 1
Pearson NaN 0 1
running
Start: AIC=64
~Class * Sex * Age * Survived
Error in loglin(data, margins, start = start, fit = fitted, param = param,
:
subscript out of bounds
Enter a frame number, or 0 to exit
1: local({
X <- Titanic
print(class(X))
Y <- paste("~", paste(names(dimnames(X)), collapse = "*"))
print(Y)
sm <- loglm(as.formula(Y), data = X
2: eval.parent(substitute(eval(quote(expr), envir)))
3: eval(expr, p)
4: eval(expr, envir, enclos)
5: eval(quote({
X <- Titanic
print(class(X))
Y <- paste("~", paste(names(dimnames(X)), collapse = "*"))
print(Y)
sm <- loglm(as.formula(Y), dat
6: eval(expr, envir, enclos)
7: #1: step(sm, direction = "backward")
8: #1: drop1(fit, scope$drop, scale = scale, trace = trace, k = k, ...)
9: #1: drop1.default(fit, scope$drop, scale = scale, trace = trace, k = k,
...)
10: #1: update(object, as.formula(paste("~ . -", tt)), evaluate = FALSE)
11: #1: update.loglm(object, as.formula(paste("~ . -", tt)), evaluate =
FALSE)
12: #1: eval.parent(call)
13: #1: eval(expr, p)
14: #1: eval(expr, envir, enclos)
15: #1: loglm(formula = ~Class + Sex + Age + Survived + Class:Sex +
Class:Age + Sex:Age + Class:Survived + Sex:Survived + Age:Survived +
Class:Sex:Age + Class:
16: #1: loglm1(formula, data, ..., .call = .call, .formula = .formula)
17: #1: loglm1.default(formula, data, ..., .call = .call, .formula =
.formula)
18: #1: loglin(data, margins, start = start, fit = fitted, param = param,
eps = eps, iter = iter, print = print)
Selection: 0
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