如何从特定单词后的字符串中提取

Question

I have this string :

string <-"DIS_S_CD_EFS-NO_PCI-CD_ACT_CG-SOM_MT_ECT_CVE"

I need to extract only SOM_MT_ECT_CVE from it.

So for me the key word is SOM (identify its position ).

I tried using this :

d <-substr(gregexpr(pattern ='SOM',"DIS_S_CD_EFS-NO_PCI-CD_ACT_CG-SOM_MT_ECT_CVE"),
           nchar("DIS_S_CD_EFS-NO_PCI-CD_ACT_CG-SOM_MT_ECT_CVE"),"DIS_S_CD_EFS-NO_PCI-CD_ACT_CG-SOM_MT_ECT_CVE")

But it return NA values.

Answer 1

One option is sub to match characters ( .* ) until 'SOM', capture the 'SOM' to the rest of the characters in a group ( (...) ) and in the replacement use the backreference ( \\\\1 ) of the captured group

sub(".*(SOM_.*)", "\\1", string)
#[1] "SOM_MT_ECT_CVE"

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Or using stringr

library(stringr)
str_extract(string, "SOM.*")
#[1] "SOM_MT_ECT_CVE"

Answer 2

You can split on the hyphen and get the last word, ie

tail(strsplit(string, '-', fixed = TRUE)[[1]], 1)
#[1] "SOM_MT_ECT_CVE"

Or with word from stringr ,

stringr::word(string, -1, sep = '-')
#[1] "SOM_MT_ECT_CVE"