Hi,
I've run into a problem calling the step function from within a function; I
sent this to the R development list first, but the moderator said it was better
suited to R help. My OS is Windows 7 and I'm using R version 3.2.3.
Here's a simple function to help reproduce the error:
> test.FN
function(dfr, scope, k=2){
temp.lm=lm(scope$lower, data=dfr)
step(temp.lm, scope=scope$upper, k=k)
}
And here's the code that gives the error when calling the function above:
# Begin by setting the rng seed.
> set.seed(523)
# Generate a design matrix and response.
> X.des=matrix(abs(rnorm(50*20, sd=4)), nrow=50)
> Y=20 + X.des[, 1:3] %*% matrix(c(3, -4, 2), nrow=3) + rnorm(50)
> X.des=cbind(as.data.frame(X.des), Y)
# Create the lower and upper formula components of a list.
> test.scope=list(lower=as.formula(Y ~ 1), upper=as.formula(paste("Y ~ ",
paste(names(X.des)[1:20], collapse=" + "), sep="")))
# Run 'test.FN'.
> test.FN(dfr=X.des, scope=test.scope)
Start: AIC=257.58
Y ~ 1
Error in is.data.frame(data) : object 'dfr' not found
> traceback()
11: is.data.frame(data)
10: model.frame.default(formula = Y ~ V1 + V2 + V3 + V4 + V5 + V6 +
V7 + V8 + V9 + V10 + V11 + V12 + V13 + V14 + V15 + V16 +
V17 + V18 + V19 + V20, data = dfr, drop.unused.levels = TRUE)
9: stats::model.frame(formula = Y ~ V1 + V2 + V3 + V4 + V5 + V6 +
V7 + V8 + V9 + V10 + V11 + V12 + V13 + V14 + V15 + V16 +
V17 + V18 + V19 + V20, data = dfr, drop.unused.levels = TRUE)
8: eval(expr, envir, enclos)
7: eval(fcall, env)
6: model.frame.lm(fob, xlev = object$xlevels)
5: model.frame(fob, xlev = object$xlevels)
4: add1.lm(fit, scope$add, scale = scale, trace = trace, k = k,
...)
3: add1(fit, scope$add, scale = scale, trace = trace, k = k, ...)
2: step(temp.lm, scope = scope$upper, k = k) at #3
1: test.FN(dfr = X.des, scope = test.scope)
The call to the traceback function indicates add1 doesn't see the dataframe dfr
passed to test.FN. The step function runs fine when I do everything in the
global environment without using test.FN. I know the lexical scoping rules are
different for objects involving model formulae, but despite a fair amount of
experimentation, I haven't found any way to make the step / add1 functions see
the dataframe that's passed to test.FN. Any help would be greatly appreciated.
Thanks,
Paul Louisell
Statistical Specialist
paul.louis...@pw.utc.com<mailto:paul.louis...@pw.utc.com>
860-565-8104
Still, tomorrow's going to be another working day, and I'm trying to get some
rest.
That's all, I'm trying to get some rest.
Paul Simon, "American Tune"
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