[R] replace values in one df by values from key pairs in another df

[arnaud gaboury]

I have been searching for a while now, but can't put all pieces of the
puzzle together.

Goal : I want to replace all these kinds of patterns <@U032FHV3S> by
this <@agreenmamba>. In a more generic way, it is replacing 'id' by
user 'name'.

I have two df:
The first, 'history', is some message history where I want to do the
replacement. It is a chat history log,
The second one, idName, is a list of id:name. All are unique. This df
rows are exctracted from a bigger one called 'users' this way :
users[users$id %in% ext].


Please find below my two data.frames:
-------------------------------------------------------------------------
history <- structure(list(name = c("xaeth", "agreenmamba", "poisonivy",
"agreenmamba", "cruzecontrol", "poisonivy", "poisonivy", "vairis",
"vairis", "poisonivy"), text = c("and people told that agent their
geocities experience would never amount to anything (the convo
yesterday) ",
"<@U032FHV3S> <http://youtu.be/oGIFublvDes>", "for me there is no such
question",
"<@U03AEKWTL|agreenmamba> uploaded a file:
<https://enlightened.slack.com/files/agreenmamba/F03KGRF3W/screenshot_2015-02-09-14-31-15.png|regarding:
should I stay or should I go?>",
"Lol.", "ha ha sorry", "some testing with my irc client", "anybody
knows how does \"Passcode circuitry too hot. Wait for cool down to
enter another passcode.\" works?",
"what is the cooldown time or how does it work...;", "<@U03AEKYL4>:
what app are you talking about ?"
)), .Names = c("name", "text"), class = c("data.table", "data.frame"
), row.names = c(NA, -10L)
--------------------------------------------------------------
idName <- structure(list(id = c("U03AEKWTL", "U032FHV3S", "U03AEKYL4"),
    name = c("agreenmamba", "poisonivy", "vairis")), .Names = c("id",
"name"), sorted = "name", class = c("data.table", "data.frame"
), row.names = c(NA, -3L))

--------------------------------------------------------------------

1- I can find the pattern to be replaced in history this way :

ext <- regmatches(history$text,regexpr('(?<=<@)[^|]{9}(?=>|)',history$text,
perl = T)
> ext
[1] "U032FHV3S" "U03AEKWTL" "U03AEKYL4"

2- I can select the pairs id:name in my 'users' df:

> idName=users[users$id %in% ext]
          id        name
1: U03AEKWTL agreenmamba
2: U032FHV3S   poisonivy
3: U03AEKYL4      vairis

3-  i can write a loop to make the changes:

> hist.txt <- history$text
> for (i in 1:3){hist.txt <- gsub(ext[i],idName[[2]][i], hist.txt, perl = T)}

But this will not work because of two things:
- 'idName' is not ordered the same way as 'ext'
- if a users speak twice it will leave with with some NA

May you have some hints how to process ?
I was thinking of maybe using sapply(myFun) to my 'history' df where
myFun would be the replacement process.
OR something like with assigning in my env each 'id' to its corresponding 'name'


Thank you for help