[R] automatic SI prefixes as ticklabels on axis

[Rui Barradas]

Hello,

You can use your function with 'lapply'


getSIstring(2e7)
getSIstring(2e-8)

lapply(c(2e7, 2e-8, 1234), getSIstring)         # as a list
unlist(lapply(c(2e7, 2e-8, 1234), getSIstring)) # as a character vector

or you can include the 'lapply' in the function body


getSIstring2 <- function(x){
  f <- function(x){
    i=0
    repeat{
        i=i+1
        if (x > prefixpairs$factor[i]) {
            sistring <- paste(x/prefixpairs$factor[i],
prefixpairs$prefix[i])
            break
        }
        if (i >= length(prefixpairs$factor)) break
    }
    sistring
  }
  prefixpairs <-
data.frame(factor=c(1e24,1e21,1e18,1e15,1e12,1e9,1e6,1e3,1e0,
                              1e-3,1e-6,1e-9,1e-12,1e-15,1e-18,1e-21,1e-24),
                            prefix=c("Y", "Z", "E", "P", "T", "G", "M", "k",
" ",
                              "m", "u", "n", "p", "f", "a", "z", "y"))
  x <- sort(x)  # needed?
  unlist(lapply(x, f))
}

getSIstring2(2e7)
getSIstring2(2e-8)
getSIstring2(c(2e7, 2e-8))
getSIstring2(c(2e7, 2e-8, 1234))


I've included the value 1234 because I coudn't understand wether it could be
passed to the function.
To return '1 k', use a 'round' inside the paste to round the division value.
See ?round

Rui Barradas


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