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rshinystring-concatenationbidiurdu

how to properly concatenate bidi strings in r?

I want to add markup to (Urdu language) text that is written right to left. I am trying to use gsub for the purpose but everything I have tried so far does not produce the desired output

text <- "یہ جملہ ایک مثال کے لیے استعمال کیا جا رہا ہے"
pattern <- "کیا جا"
replaceWith <- paste0("<somemark>", pattern, "</somemark>")
gsub(pattern, replaceWith, text)

gsub returns the following 

یہ جملہ ایک مثال کے لیے استعمال <somemark>کیا جا</somemark> رہا ہے

desired output .

enter image description here

How can I acheive the desired output?

Note: I could not even properly typeset the desired output in my post, I had to rely on an image instead.

Update: Although mysub function below correctly concatenates the strings(in console), I continue to face the problem of incorrect order of text in shiny app. 

mysub <- function(text, pattern){
beforePattern <- substr(text, 1, regexpr(pattern, text)[1]-1)
afterPattern <- substr(text, regexpr(pattern,text)[1] + nchar(pattern), nchar(text))
result <- paste(afterPattern, replaceWith, beforePattern)
result
}
Solution

  • I gave it a try . I did take the liberty of hard coding the args instead of reading from session, though. 

    Server: 

output$mysub <- function(){ # (text=NULL, pattern=NULL)

text <- "یہ جملہ ایک مثال کے لیے استعمال کیا جا رہا ہے"
pattern <- "کیا جا"

Encoding(text) <- "UTF-8"
Encoding(pattern) <- "UTF-8"

print(text)

beforePattern <- substr(text, 1, regexpr(pattern, text)[1]-1)
afterPattern <- substr(text, regexpr(pattern,text)[1] + nchar(pattern), nchar(text))

replaceWith <- paste0("<somemark>", pattern, "</somemark>")
result <- paste(afterPattern, replaceWith, beforePattern)

# result <- paste( beforePattern, replaceWith, afterPattern)
# Encoding(result) <- "UTF-8"
print(length(result))
print(result)

return(result)
}


# ui.R: 

h2( textOutput("mysub") )

    The output I got on shiny webpage was : bidi text output