I am trying to remove a block of text that wraps around what I want to keep. So I wanted to assign variables since the text can be long. This is an example of what I am trying to do. [Doesn't remove the text]
Text<-'This is an example text [] test'
topheader<-'This'
bottomheader<-'test'
gsubfn(".", list(topheader = "", bottomheader = ""), Text)
[1] "This is an example text [] test"
Goal: "is an example text []"
1) gsubfn There are several problems here:
the regular expression in gsubfn (and in gsub) must match the string you want to process but a dot matches only a single character so it can never match This or test which are 4 character strings. Use "\\w+" instead.
In list(a = x) the a must be a constant, not a variable. Write out the names explicitly or use setNames instead if they are in variables.
Thus to fix up the code in the question:
library(gsubfn)
trimws(gsubfn("\\w+", list(This = "", text = ""), Text))
## [1] "is an example [] test"
or in terms of the header variables:
L <- setNames(list("", ""), c(topheader, bottomheader))
trimws(gsubfn("\\w+", L, Text))
## [1] "is an example [] test"
Note that this will replace any occurrence of topheader and bottomheader and not just ones at the start and end; however, this seems to be the closest to your code that is likely sufficient.
2) sub Another possibility is this simple sub
sub("^This (.*) text$", "\\1", Text)
[1] "is an example [] test"
or in terms of the header variables:
pat <- sprintf("^%s (.*) %s$", topheader, bottomheader)
sub(pat, "\\1", Text)
## [1] "is an example [] test"
Update: Fixed (1)