R Regex matching of mentions in twitts. with Power Query and R

RTwitts.m

let
    Source = Csv.Document(File.Contents("RTwitterSample.csv"),[Delimiter=",", Columns=2, Encoding=1252, QuoteStyle=QuoteStyle.Csv]),
    twitts = Table.PromoteHeaders(Source, [PromoteAllScalars=true]),
    RScript = R.Execute("temp<-dataset#(lf)pattern<-""[#@]\\w+""#(lf)temp$mention<-sapply(temp$text,function(x) toString(regmatches(x, regexpr(pattern, x))))",[dataset=twitts ]),
    out = RScript{[Name="temp"]}[Value]
in
    out