I believe this has to do terms() making "term.labels" (hence the dimnames
of "factors")
with deparse(), so that the backquotes are included for non-syntactic
names. The backquotes
are not in the column names of the input data.frame (nor model frame) so
you get a mismatch
when subscripting the data.frame or model.frame with elements of
terms()$term.labels.
I think you can avoid the problem by adding right after
ll <- attr(Terms, "term.labels")
the line
ll <- gsub("^`|`$", "", ll)
E.g.,
> d <- data.frame(check.names=FALSE, y=1/(1:5), `b$a$d`=sin(1:5)+2, `x y
z`=cos(1:5)+2)
> Terms <- terms( y ~ log(`b$a$d`) + `x y z` )
> m <- model.frame(Terms, data=d)
> colnames(m)
[1] "y" "log(`b$a$d`)" "x y z"
> attr(Terms, "term.labels")
[1] "log(`b$a$d`)" "`x y z`"
> ll <- attr(Terms, "term.labels")
> gsub("^`|`$", "", ll)
[1] "log(`b$a$d`)" "x y z"
It is a bit of a mess.
Bill Dunlap
TIBCO Software
wdunlap tibco.com
On Mon, Mar 5, 2018 at 12:55 PM, Therneau, Terry M., Ph.D. via R-devel <
r-devel@r-project.org> wrote:
> A user reported a problem with the survdiff function and the use of
> variables that contain a space. Here is a simple example. The same issue
> occurs in survfit for the same reason.
>
> lung2 <- lung
> names(lung2)[1] <- "in st" # old name is inst
> survdiff(Surv(time, status) ~ `in st`, data=lung2)
> Error in `[.data.frame`(m, ll) : undefined columns selected
>
> In the body of the code the program want to send all of the right-hand
> side variables forward to the strata() function. The code looks more or
> less like this, where m is the model frame
>
> Terms <- terms(m)
> index <- attr(Terms, "term.labels")
> if (length(index) ==0) X <- rep(1L, n) # no coariates
> else X <- strata(m[index])
>
> For the variable with a space in the name the term.label is "`in st`", and
> the subscript fails.
>
> Is this intended behaviour or a bug? The issue is that the name of this
> column in the model frame does not have the backtics, while the terms
> structure does have them.
>
> Terry T.
>
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> https://stat.ethz.ch/mailman/listinfo/r-devel
>
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