Conditional gsub replacement

Question

I have text data (in R) and want to replace some characters with other characters in a data frame. I thought this would be an easy task using strsplit on spaces and create a vector that can I can then use matching (%in%) which can then be pasted back together. But then I thought about punctuation. There's no space between the last word of a sentence and the punctuation at the end.

I figure there's probably a more simple way to achieve what I want than the convoluted mess that's becoming my code. I would appreciate direction with this problem.

#Character String
x <- "I like 346 ice cream cones.  They're 99 percent good!  I ate 46."

#Replacement Values Dataframe
  symbol text                     
1 "346"  "three hundred forty six"
2 "99"   "ninety nine"            
3 "46"   "forty six" 

#replacement dataframe
numDF <- 
data.frame(symbol = c("346","99", "46"),
           text = c("three hundred forty six", "ninety nine","forty six"),
           stringsAsFactors = FALSE)

Desired outcome:

[1] "I like three hundred forty six ice cream cones.  They're ninety nine percent good!  You ate forty six?")

EDIT: I originally entitled this conditional gsub because that what it seems like to me even though there is no gsub involved.

Answer 1

Maybe this, inspired by Josh O'Brien's answer, does it:

x <- "I like 346 ice cream cones.  They're 99 percent good!  I ate 46."
numDF <- structure(c("346", "99", "46", "three hundred forty six", "ninety nine", 
"forty six"), .Dim = c(3L, 2L), .Dimnames = list(c("1", "2", 
"3"), c("symbol", "text")))

pat <-  paste(numDF[,"symbol"], collapse="|")
repeat {
    m <- regexpr(pat, x)
    if(m==-1) break
    sym <- regmatches(x,m)
    regmatches(x,m) <- numDF[match(sym, numDF[,"symbol"]), "text"]
}
x