Unexpected symbol error in parse(text = str) with hyphen after a digit

Question

I am trying to parse a character string in R. R throws an \"unexpected symbol\" or \"unexpected end of input\" exception when there is a digit followed by a hyphen in the s

Answer 1

You can easily reproduce the parse behavior with :

str <- "3a"
parse(text = str)

parse try to parse your str as a variable name. Or, you should give an available variable name, either it should not begin with a digit or you should put it between ``. the following works :

str <- "`3a`"
parse(text = str)

and in your example , this works also :

str <- "abc12-`3def`"
parse(text = str)

Finally for your second example , it is logic that it will not work since you don't give an available expression to parse:

str <- "abc123-"  ## this will like myvar-

if your - is just a string separator, why not to transform it to _? for example:

 parse(text=gsub('-','_',str))

Answer 2

The point of parse is to turn your input text into an R-language expression. Just as if you typed

abc12-3def

at the R prompt, it would throw a syntax error, so too will parse. You can't just throw arbitrary text at it and assume it'll give you something sensible.