SI prefixes in ggplot2 axis labels

ggplot2, r

Solution

I used `library("sos"); findFn("{SI prefix}")` to find the `sitools` package.

Construct data:

bytes <- 2^seq(0,20) + rnorm(21, 4, 2)
time <- bytes/(1e4 + rnorm(21, 100, 3)) + 8
my_data <- data.frame(time, bytes)

Load packages:

library("sitools")
library("ggplot2")

Create the plot:

(p <- ggplot(data=my_data, aes(x=bytes, y=time)) +
     geom_point() +
     geom_line() +
     scale_x_log10("Message Size [Byte]", labels=f2si) +
     scale_y_continuous("Round-Trip-Time [us]"))

I'm not sure how this compares to your function, but at least someone else went to the trouble of writing it ...

I modified your code style a little bit -- semicolons at the ends of lines are harmless but are generally the sign of a MATLAB or C coder ...

edit: I initially defined a generic formatting function

si_format <- function(...) {
    function(x) f2si(x,...)
}

following the format of (e.g) `scales::comma_format`, but that seems unnecessary in this case -- just part of the deeper `ggplot2` magic that I don't fully understand.

The OP's code gives what seems to me to be not quite the right answer: the rightmost axis tick is "1000K" rather than "1M" -- this can be fixed by changing the `>1e6` test to `>=1e6`. On the other hand, `f2si` uses lower-case `k` -- I don't know whether `K` is wanted (wrapping the results in `toupper()` could fix this).

OP results (`si_vec`):

My results (`f2si`):

Problem

I often plot graphs in GNU R / ggplot for some measurements related to bytes. The builtin axis labels are either plain numbers or scientific notation, ie 1 Megabyte = 1e6. I would like SI prefixes (Kilo = 1e3, Mega=1e6, Giga=1e9, etc) instead, i.e. axis should be labelled 1.5K, 5K, 1M, 150M, 4G etc. I currently use the following code: ``` si_num <- function (x) { if (!is.na(x)) { if (x > 1e6) { chrs <- strsplit(format(x, scientific=12), split="")[[1]]; rem <- chrs[seq(1,length(chrs)-6)]; rem <- append(rem, "M"); } else if (x > 1e3) { chrs <- strsplit(format(x, scientific=12), split="")[[1]]; rem <- chrs[seq(1,length(chrs)-3)]; rem <- append(rem, "K"); } else { return(x); } return(paste(rem, sep="", collapse="")); } else return(NA); } si_vec <- function(x) { sapply(x, FUN=si_num); } library("ggplot2"); bytes=2^seq(0,20) + rnorm(21, 4, 2); time=bytes/(1e4 + rnorm(21, 100, 3)) + 8; my_data = data.frame(time, bytes); p <- ggplot(data=my_data, aes(x=bytes, y=time)) + geom_point() + geom_line() + scale_x_log10("Message Size [Byte]", labels=si_vec) + scale_y_continuous("Round-Trip-Time [us]"); p; ``` I would like to know if this solution can be improved, as my one requires a lot of boilerplate code in every graph.

Original source