r - How is jitter determined in ggplot? -

i looking on documentation on jitter in ggplot while making plots, , realized don't understand argument.

it states arguments are:

width: degree of jitter in x direction. defaults 40% of resolution of data. and
height: degree of jitter in y direction. defaults 40% of resolution of data.

my question is, resolution, , how determined?

also, can override , provide value, in example below use 0.1:

geom_point(position = position_jitter(w = 0.1, h = 0.1))

what units belong 0.1? right assume proportion of resolution?

if @ source first find this:

positionjitter <- proto(position, {   objname <- "jitter"    adjust <- function(., data) {     if (empty(data)) return(data.frame())     check_required_aesthetics(c("x", "y"), names(data), "position_jitter")      if (is.null(.$width)) .$width <- resolution(data$x, 0 = false) * 0.4     if (is.null(.$height)) .$height <- resolution(data$y, 0 = false) * 0.4      trans_x <- null     trans_y <- null     if(.$width > 0) {       trans_x <- function(x) jitter(x, amount = .$width)     }     if(.$height > 0) {       trans_y <- function(x) jitter(x, amount = .$height)     }      transform_position(data, trans_x, trans_y)   }  }) 

and wouldn't know it, resolution exported function (or search sources landing here):

function (x, 0 = true)  {     if (is.integer(x) || zero_range(range(x, na.rm = true)))          return(1)     x <- unique(as.numeric(x))     if (zero) {         x <- unique(c(0, x))     }     min(diff(sort(x))) } 

so...there go!

"resolution" in context means "the smallest distance between 2 elements in vector".

this value (40% of resolution) passed on factor argument jitter, has it's own little song , dance:

the result, r, r <- x + runif(n, -a, a) n <- length(x) , amount argument (if specified).

let z <- max(x) - min(x) (assuming usual case). amount added either provided positive argument amount or otherwise computed z, follows:

if amount == 0, set <- factor * z/50 (same s).

if amount null (default), set <- factor * d/5 d smallest difference between adjacent unique (apart fuzz) x values.