因此，基本上我想要做的就是删除包含"I"的标记之间的所有破折号.

So basically all I want to do is to remove all the dashes between markers containing "I".

如果您的案子听起来很简单，就可以使用环视断言.

You can use lookaround assertions if your case is as simple as it sounds.

gsub('(?<=I\\d)-(?=I\\d)', '', string, perl = TRUE)
# [1] "FA-I2I2I2-EX-I2I3-FA-I1I2-TR-I1I2-FA-I3I1-FAFANR-I3I2-TR-I1I2I1I2-FA-I2I1I3-FAQU-I1I2I2I2-NR-I2I2-NR-I1I2I1-NR-I3-QU-I2I3-QUNR-I2I1-NRQUQU-I2I1-EX"