remove value using grepl

Question

I am trying to remove retweets (strings that start with RT) from a dataset, but my grepl command doesn't seem to work right.

this works fine:

grepl("[^rt|RT][:alnum]",c("RT hi","rt boo","rtlolo","im goodRT"),ignore.case=T)

this fails. Why?

data<-structure(list(data = c("RT @4MySquad: This makes me sick!\\n#whiteprivilege\\n#BlackLivesMatter \\n#Policestate https:\\/\\/t.co\\/nDL0AHwWTd", 
                              "RT @weaselzippers: D.C. Police Want Help Identifying #BlackLivesMatter Supporters Who Beat And Left Hero Marine For Dead\\u2026 https:\\/\\/t.co\\/tbmO\\u2026", 
                              "RT @vicegandako: #PrayForMannyPacquiao #LoveWins", "\\Dig out of the binaries of right and wrong\\ - #BlackLivesMatter at Mizzou", 
                              "Even Democrats think #Bernie 's ideas are unrealistic #insane #UNLV #BigBangTheory #Hillary2016 #blacklivesmatter https:\\/\\/t.co\\/ITDyXoAvtK", 
                              "RT @eelawl1966: Former NAACP President Ben Jealous endorses Bernie Sanders\\n#BlackLivesMatter #BLM #Bernie2016 \\n https:\\/\\/t.co\\/Qom1KMwLHs", 
                              "#SayNoToHillary #NoMoreClintons #FeelTheBern #BernieSanders #BlackLivesMatter #Disabled4Bernie #Women4Bernie... https:\\/\\/t.co\\/I8F21ilJgv", 
                              "RT @JoshuaMannery: #BlackLivesMatter \\ud83d\\udc4a\\ud83c\\udffd https:\\/\\/t.co\\/tcEITKKGhd", 
                              "lang:und", "@FoxNews Did he not say, \\Yes\\? Hopefully this story won't gain traction bc it's not reflective of the #blacklivesmatter movement", 
                              "President Barack Obama Is Doing Big Things With Cuba + #BlackLivesMatter https:\\/\\/t.co\\/6gEJreOiUc", 
                              "RT @Uberarabic: \\u0644\\u0644\\u0639\\u0644\\u0645 \\u0639\\u0642\\u0648\\u0628\\u0629 \\u0627\\u0644\\u0645\\u062b\\u0644\\u064a\\u064a\\u0646 \\u0641\\u064a \\u062c\\u0645\\u064a\\u0639 \\u0627\\u0644\\u062f\\u0627\\u064a\\u0627\\u0646\\u0627\\u062a \\u0627\\u0644\\u0633\\u0645\\u0627\\u0648\\u064a\\u0629 \\u0647\\u064a \\u0627\\u0644\\u0642\\u062a\\u0644\\n\\n#LoveWins", 
                              "RT @AishaYesufu: Let's not forget 219#ChibokGirls still in captivity today 676 days \\n#NeverToBeForgotten #CryingToBeRescued #BringBackOurGi\\u2026", 
                              "RT @arctic_matters: Chukchi Sea. #LoveWins https:\\/\\/t.co\\/gH8KZgVZk3", 
                              ". @DoubleFine r u joking, tim u know the servers aren't working you dumb asshole #gamergate", 
                              "RT @realkingcalii: #BlackLivesMatter Kendrick Lamar \\Alright\\ - https:\\/\\/t.co\\/amlRn0fKsA", 
                              "RT @DreamersMOMS: Community representing #CCA &amp; @geogroups making dirty $$$$ w\\/immigrants. #WeAreFlorida #not1more #immigration https:\\/\\/t.c\\u2026", 
                              "id_str:700012325831581696", "RT @DreamersMOMS: Con compa\\u00f1eras de Carolina del Norte apoy\\u00e1ndonos en #Tallahassee. #ProteccionNoDeportation #Not1More @grisalonso https:\\/\\/\\u2026", 
                              "RT @IkeIsaacson2: Hey #blacklivesmatter this is a hate crime done by racists in your name. https:\\/\\/t.co\\/6uGSXAJcrM"
)), .Names = "data", row.names = c(NA, 20L), class = "data.frame")

data[grepl("[^rt|RT][:alnum]",data,ignore.case=T)]

this question also uses Twitter data, but has a different approach

Answer 1

We specify the pattern as characters that start (^) with RT followed by one or more spaces (\\s+) and as the ignore.case = TRUE, it will also get elements that start with rt followed by space.

grepl("^RT\\s+",c("RT hi","rt boo","rtlolo","im goodRT"), ignore.case=TRUE)
#[1] TRUE TRUE FALSE FALSE

grep("^RT\\s+", data$data, ignore.case=TRUE, value = TRUE)
 #[1] "RT @4MySquad: This makes me sick!\\n#whiteprivilege\\n#BlackLivesMatter \\n#Policestate https:\\/\\/t.co\\/nDL0AHwWTd"                                                                                                                                                                                                                                                                  
 #[2] "RT @weaselzippers: D.C. Police Want Help Identifying #BlackLivesMatter Supporters Who Beat And Left Hero Marine For Dead\\u2026 https:\\/\\/t.co\\/tbmO\\u2026"                                                                                                                                                                                                                         
 #[3] "RT @vicegandako: #PrayForMannyPacquiao #LoveWins"                                                                                                                                                                                                                                                                                                                                       
 #[4] "RT @eelawl1966: Former NAACP President Ben Jealous endorses Bernie Sanders\\n#BlackLivesMatter #BLM #Bernie2016 \\n https:\\/\\/t.co\\/Qom1KMwLHs"                                                                                                                                                                                                                                      
 #[5] "RT @JoshuaMannery: #BlackLivesMatter \\ud83d\\udc4a\\ud83c\\udffd https:\\/\\/t.co\\/tcEITKKGhd"                                                                                                                                                                                                                                                                                        
 #[6] "RT @Uberarabic: \\u0644\\u0644\\u0639\\u0644\\u0645 \\u0639\\u0642\\u0648\\u0628\\u0629 \\u0627\\u0644\\u0645\\u062b\\u0644\\u064a\\u064a\\u0646 \\u0641\\u064a \\u062c\\u0645\\u064a\\u0639 \\u0627\\u0644\\u062f\\u0627\\u064a\\u0627\\u0646\\u0627\\u062a \\u0627\\u0644\\u0633\\u0645\\u0627\\u0648\\u064a\\u0629 \\u0647\\u064a \\u0627\\u0644\\u0642\\u062a\\u0644\\n\\n#LoveWins"
 #[7] "RT @AishaYesufu: Let's not forget 219#ChibokGirls still in captivity today 676 days \\n#NeverToBeForgotten #CryingToBeRescued #BringBackOurGi\\u2026"                                                                                                                                                                                                                                   
 #[8] "RT @arctic_matters: Chukchi Sea. #LoveWins https:\\/\\/t.co\\/gH8KZgVZk3"                                                                                                                                                                                                                                                                                                               
 #[9] "RT @realkingcalii: #BlackLivesMatter Kendrick Lamar \\Alright\\ - https:\\/\\/t.co\\/amlRn0fKsA"                                                                                                                                                                                                                                                                                        
#[10] "RT @DreamersMOMS: Community representing #CCA & @geogroups making dirty $$$$ w\\/immigrants. #WeAreFlorida #not1more #immigration https:\\/\\/t.c\\u2026"                                                                                                                                                                                                                           
#[11] "RT @DreamersMOMS: Con compa\\u00f1eras de Carolina del Norte apoy\\u00e1ndonos en #Tallahassee. #ProteccionNoDeportation #Not1More @grisalonso https:\\/\\/\\u2026"                                                                                                                                                                                                                     
#[12] "RT @IkeIsaacson2: Hey #blacklivesmatter this is a hate crime done by racists in your name. https:\\/\\/t.co\\/6uGSXAJcrM"