[R] Regex - subsetting parts of a file name.

[arnaud gaboury]

A directory is full of data.frames cache files. All these files have
the same pattern:

df.some_name.RData

my.cache.list <- c("df.subject_test.RData", "df.subject_train.RData",
"df.y_test.RData",
"df.y_train.RData")

I want to keep only the part inside the two points. After lots of
headache using grep() when trying something like this:

grep('.(.*?).','df.subject_test.RData',value=T)

 I couldn't find a clean one liner and found this workaround:

my.cache.list <- gsub('df.','',my.cache.list)
my.cache.list <- gsub('.RData','',my.cache.list)

The two above commands do the trick, but a clean one line with some
regex expression would be a more "elegant" way.

Does anyone have any suggestion ?

TY for help