[R] Regexpr with "."

[Uwe Ligges]

Thompson, Trevor wrote:

> I'm trying to use the regexpr function to locate the decimal in a character
> string.  Regardless of the position of the decimal, the function returns 1.
> For example,
> 
> 
>>regexpr(".", "Female.Alabama")
> 
> [1] 1
> attr(,"match.length")
> [1] 1
> 
> In trying to figure out what was going on here, I tried the below command:
> 
> 
>>gsub(".", ",", "Female.Alabama")
> 
> [1] ",,,,,,,,,,,,,,"
> 
> It looks like R is treating every character in the string as if it were
> decimal.  I didn't see anything in the help file about "." being some kind
> of special character.  Any idea why R is treating a decimal this way in
> these functions?   Any suggestions how to get around this?
> 
> Thanks for any suggestions.
> 
> -Trevor
>  
> 
> 
> 	[[alternative HTML version deleted]]
> 
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Think about the meaning of "." in regular expression (it needs to be 
escaped as being a special character!):

  gsub("\\.", ",", "Female.Alabama")
or
  regexpr("\\.", "Female.Alabama")

Uwe Ligges