On 18/09/2019 8:43 a.m., Huzefa Khalil wrote:
Hello R-users,
I have been running a script which produces objects based on the
column names of a data.frame. The column names are of the form CB_1-1,
CB_1-2, etc. Now this calculation was rather long and memory
intensive, so I would rather not have to do it again after fixing the
column names using "make.names". As a consequence, I am left with a
bunch of R objects with `-` in the name.
Accessing them is proving challenging and any help would be appreciated.
Reproducible example:
`cb_1-2` <- "hello world"
t <- "cb_1-2"
t <- as.name(t)
t <- eval(parse(text = t))
Error in eval(parse(text = t)) : object 'cb_1' not found
After t <- as.name(t), you already have language: no need to parse it
again. So
eval(t)
works. If you have more complicated expressions, use call() to set them
ụp. For example, call("paste0", t, "!") evaluates to
paste0(`cb_1-2`, "!")
and evaluating that expression via
eval(call("paste0", t, "!"))
gives
[1] "hello world!"
Don't go back and forth between language objects and text
representations of them, because it's hard to do that without
introducing changes. In other words, don't use eval(parse()).
Duncan Murdoch
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