- So you want to translate SI unit abbreviations (‘K’,’M’,…) into exponents, and thus numerical powers-of-ten.
Given that all units are single-letter, and the exponents are uniformly-spaced powers of 10**3, here’s working code that handles ‘Kilo’…’Yotta’, and any future exponents:
> 10 ** (3*as.integer(regexpr('T', 'KMGTPEY')))
[1] 1e+12
Then just multiply that power-of-ten by the decimal value you have.
- Also, you probably want to detect and handle the ‘no-match’ case for unknown letter prefixes, otherwise you’d get a nonsensical
-1*3
> unit_to_power <- function(u) {
exp_ <- 10**(as.integer(regexpr(u, 'KMGTPEY')) *3)
return (if(exp_>=0) exp_ else 1)
}
-
Now if you want to case-insensitive-match both ‘k’ and ‘K’ to Kilo (as computer people often write, even though it’s technically an abuse of SI), then you’ll need to special-case e.g with if-else ladder/expression (SI units are case-sensitive in general, ‘M’ means ‘Mega’ but ‘m’ strictly means ‘milli’ even if disk-drive users say otherwise; upper-case is conventionally for positive exponents). So for a few prefixes, @DanielV’s case-specific code is better.
-
If you want negative SI prefixes too, use
as.integer(regexpr(u, 'zafpnum@KMGTPEY')-8)where@is just some throwaway character to keep uniform spacing, it shouldn’t actually get matched. Again if you need to handle non-power-of-10**3 units like ‘deci’, ‘centi’, will require special-casing, or the general dict-based approach WeNYoBen uses. -
base::regexpris not vectorized also its performance is bad on big inputs, so if you want to vectorize and get higher-performance usestringr::str_locate.