Is there an R library or function for formatting international currency strings? - r

Question

Here's a snippet of the JSON data I'm working with:
{
"item" = "Mexican Thing",
...
"raised": "19",
"currency": "MXN"
},
{
"item" = "Canadian Thing",
...
"raised": "42",
"currency": "CDN"
},
{
"item" = "American Thing",
...
"raised": "1",
"currency": "USD"
}
You get the idea.
I'm hoping there's a function out there that can take in a standard currency abbreviation and a number and spit out the appropriate string. I could theoretically write this myself except I can't pretend like I know all the ins and outs of this stuff and I'm bound to spend days and weeks being surprised by bugs or edge cases I didn't think of. I'm hoping there's a library (or at least a web api) already written that can handle this but my Googling has yielded nothing useful so far.
Here's an example of the result I want (let's pretend "currency" is the function I'm looking for)
currency("USD", "32") --> "$32"
currency("GBP", "45") --> "£45"
currency("EUR", "19") --> "€19"
currency("MXN", "40") --> "MX$40"

Answer 1

Assuming your real json is valid, then it should be relatively simple. I'll provide a valid json string, fixing the three invalid portions here: = should be :; ... is obviously a placeholder; and it should be a list wrapped in [ and ]:
js <- '[{
"item": "Mexican Thing",
"raised": "19",
"currency": "MXN"
},
{
"item": "Canadian Thing",
"raised": "42",
"currency": "CDN"
},
{
"item": "American Thing",
"raised": "1",
"currency": "USD"
}]'
with(jsonlite::parse_json(js, simplifyVector = TRUE),
paste(raised, currency))
# [1] "19 MXN" "42 CDN" "1 USD"
Edit: in order to change to specific currency characters, don't make this too difficult: just instantiate a lookup vector where "USD" (for example) prepends "$" and appends "" (nothing) to the raised string. (I say both prepend/append because I believe some currencies are always post-digits ... I could be wrong.)
pre_currency <- Vectorize(function(curr) switch(curr, USD="$", GDP="£", EUR="€", CDN="$", "?"))
post_currency <- Vectorize(function(curr) switch(curr, USD="", GDP="", EUR="", CDN="", "?"))
with(jsonlite::parse_json(js, simplifyVector = TRUE),
paste0(pre_currency(currency), raised, post_currency(currency)))
# [1] "?19?" "$42" "$1"
I intentionally left "MXN" out of the vector here to demonstrate that you need a default setting, "?" (pre/post) here. You may choose a different default/unknown currency value.
An alternative:
currency <- function(val, currency) {
pre <- sapply(currency, switch, USD="$", GDP="£", EUR="€", CDN="$", "?")
post <- sapply(currency, switch, USD="", GDP="", EUR="", CDN="", "?")
paste0(pre, val, post)
}
with(jsonlite::parse_json(js, simplifyVector = TRUE),
currency(raised, currency))
# [1] "?19?" "$42" "$1"