How do I transform a stock ticker to a unique integer in R?

Question

How do I transform a stock ticker to a unique integer in R?

This is useful, for example, when matching two data bases based on stock ticker symbols. The code should work for ordinary equity tickers (capital letters, 1-4 characters in length).

Answer 1

hash.ticker <- Vectorize( function(s, M=length(letters), MAXCHARS=4) {
    v <- utf8ToInt(s) - utf8ToInt("@")
    if (length(v)<MAXCHARS) v <- c(v,rep(0,MAXCHARS-length(v)))
    stopifnot( all( (v >= 0) & (v <= M) ) ) ## need 0 to account for empty (0)                                                                                                           
    sum( v * (M)^(0:(length(v)-1)) )
})

print( hash.ticker( c("A", "Z", "AA", "ZZ", "ZZZZ") ) )
 A      Z     AA     ZZ   ZZZZ 
 1     26     27    702 475254