Extract a substring according to a pattern

Question

Suppose I have a list of string   string   c  G1 E001    G2 E002    G3 E003     Now I hope to get a vector of string that contains only the parts after the colon      i e substring   c E001 E002 E003    Is there a convenient way in R to do this  Using substr

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The unglue package provides an alternative  no knowledge about regular expressions is required for simple cases  here we d do      install packages  unglue   library unglue  string   c  G1 E001    G2 E002    G3 E003   unglue vec string   x   y    var    y     gt   1   E001   E002   E003    Created on 2019-11-06 by the reprex package  v0 3 0   More info   https   github com moodymudskipper unglue blob master README md

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Here is another simple answer  gsub            string

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Here are a few ways  1  sub sub  quot     quot    quot  quot   string      1   quot E001 quot   quot E002 quot   quot E003 quot   2  strsplit sapply strsplit string   quot   quot     quot   quot   2      1   quot E001 quot   quot E002 quot   quot E003 quot   3  read table read table text   string  sep    quot   quot   as is   TRUE  V2     1   quot E001 quot   quot E002 quot   quot E003 quot   4  substring This assumes second portion always starts at 4th character  which is the case in the example in the question   substring string  4      1   quot E001 quot   quot E002 quot   quot E003 quot   4a  substring regex If the colon were not always in a known position we could modify  4  by searching for it  substring string  regexpr  quot   quot   string    1   5  strapplyc strapplyc returns the parenthesized portion  library gsubfn  strapplyc string   quot       quot   simplify   TRUE      1   quot E001 quot   quot E002 quot   quot E003 quot   6  read dcf This one only works if the substrings prior to the colon are unique  which they are in the example in the question    Also it requires that the separator be colon  which it is in the question    If a different separator were used then we could use sub to replace it with a colon first   For example  if the separator were   then string  lt - sub  quot   quot    quot   quot   string  c read dcf textConnection string        1   quot E001 quot   quot E002 quot   quot E003 quot   7  separate 7a  Using tidyr  separate we create a data frame with two columns  one for the part before the colon and one for after  and then extract the latter  library dplyr  library tidyr  library purrr   DF  lt - data frame string  DF   gt      separate string  into   c  quot pre quot    quot post quot      gt      pull  quot post quot       1   quot E001 quot   quot E002 quot   quot E003 quot   7b  Alternately separate can be used to just create the post column and then unlist and unname the resulting data frame  library dplyr  library tidyr   DF   gt      separate string  into   c NA   quot post quot      gt      unlist   gt     unname     1   quot E001 quot   quot E002 quot   quot E003 quot   8  trimws We can use trimws to trim word characters off the left and then use it again to trim the colon  trimws trimws string   quot left quot    quot   w quot     quot left quot    quot   quot       1   quot E001 quot   quot E002 quot   quot E003 quot   Note The input string is assumed to be  string  lt - c  quot G1 E001 quot    quot G2 E002 quot    quot G3 E003 quot

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For example  using gsub or sub      gsub              1  string       1   E001   E002   E003

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If you are using data table then tstrsplit   is a natural choice   tstrsplit string        2    1   E001   E002   E003

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Late to the party  but for posterity  the stringr package  part of the popular  tidyverse  suite of packages  now provides functions with harmonised signatures for string handling   string  lt - c  G1 E001    G2 E002    G3 E003     match string to keep stringr  str extract string   string  pattern    E 0-9        1   E001   E002   E003     replace leading string with    stringr  str remove string   string  pattern              1   E001   E002   E003

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This should do   gsub   A-Z  1-9         string    gives   1   E001   E002   E003

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Another method to extract a substring library stringr  substring  lt - str extract string  regex  quot    lt       quot      1   quot E001 quot   quot E002 quot   quot E003      lt      look behind the colon

[regex] Extract a substring according to a pattern

Examples related to regex

Examples related to r

Examples related to substr