使用 grepl() 函数在 R 中进行模式匹配

Question

I have below pattern match -

grepl("Close_[a-zA-Z]{0,}_{0,1}ASE_[a-zA-Z]{0,}_{0,1}", "Close_ASE_RS____")
#TRUE

R returns this as affirmative match. Shouldn't it be FALSE since I have "____" which has more than 1 repetition of "_" , but in my pattern I put only max 1 match through "_{0,1}"

Any pointer why it is happening will be highly helpful.

Thanks,

Answer 1

Try indicating the string ends after your initial pattern:

grepl("Close_[a-zA-Z]{0,}_{0,1}ASE_[a-zA-Z]{0,}_{0,1}$", "Close_ASE_RS____")

# [1] FALSE

Otherwise you can put anything after the initial underscore following RS and it will match it.

Answer 2

We can use word boundary

grepl("Close_[a-zA-Z]{0,}_{0,1}ASE_[a-zA-Z]{0,}_{0,1}\\b", "Close_ASE_RS____")
#[1] FALSE