New Post: how to call function from r script

First:

source("D:\something.R")

cannot work. You have a single backslash character. Use:

source(@"D:\something.R")

Probably the same thing with the following, as an aside:

"sentence = gsub('\\d+', '', sentence)" +

besides the whole string you build is not a valid function declaration: you have no semi-colon or newline separator between statements.

source(@"D:\something.R")
var sentiment = engine.GetSymbol("score.sentiment").AsFunction();

You'll find sample code on how to invoke functions for instance in https://github.com/jmp75/rdotnet/blob/master/RDotNet.Tests/RFunctionsTest.cs