The dollar sign is convenient to write, but allows for partial matching,
which we don't often want. This function takes a file and changes all dollar
signs to double brackets with names in quotations instead. Note that this
-function will incorrectly convert text enclosed in backticks that includes a dollar sign.
-Note also that if a dollar sign is within a text
-string enclosed with quotation marks, it will also not convert correctly and
-so will exit on error.
-(for example, "See test$name" would become
-"See test[["name"]]", which is not parsable R code due to 2 sets of quotation
-marks.)
+function will incorrectly convert text enclosed in backticks that includes a dollar sign.