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Allow functional limits in continuous scales #2334

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Merged
merged 5 commits into from
Apr 24, 2019
Merged

Allow functional limits in continuous scales #2334

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3d2e6f7
Allow functional limits in continous scales
econandrew Nov 11, 2017
302e697
merge upstream/master into allow-functional-limits
dpseidel Apr 13, 2019
c86d643
clarify get_limits conditionals, add tests.
dpseidel Apr 13, 2019
4cd6c4f
minor comment change
dpseidel Apr 13, 2019
184bd2c
revert NEWS nits.
dpseidel Apr 15, 2019
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6 changes: 6 additions & 0 deletions NEWS.md
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Expand Up @@ -2,6 +2,12 @@

## New features

* Continuous scale limits now accept a function, which must accept the default
/ automatic limits and return adjusted limits. This makes it possible to write
a function that e.g. ensures the limits are always a multiple of 100,
regardless of the data. It somewhat parallels the behaviour of breaks and
labels in accepting functions (@econandrew, #2307).

* ggplot2 now works on R 3.1 onwards, and uses the
[vdiffr](https://github.com/lionel-/vdiffr) package for visual testing.

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17 changes: 12 additions & 5 deletions R/scale-.r
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Expand Up @@ -107,13 +107,17 @@ Scale <- ggproto("Scale", NULL,
stop("Not implemented", call. = FALSE)
},

# if scale contains a function, apply it to the default (inverted) scale range
# if scale contains a NULL, use the default scale range
# if scale contains a NA, use the default range for that axis, otherwise
# use the user defined limit for that axis
get_limits = function(self) {
if (self$is_empty()) return(c(0, 1))

if (!is.null(self$limits)) {
if (is.function(self$limits)) {
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Since we're adding another condition here, can you please reframe the if statement along these lines:

if (is.null()) {

} else if (is.function()) {

} else if (is.numeric()) {
  
} else {
  stop("Informative error message", call. = FALSE) 
}

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I did rework this conditional to be more intuitive but since get_limits() is called by both discrete and continuous scales and can be passed character, numeric, POSIXt and now function classes, I ultimately did not add an explicit is.numeric conditional nor an error message. Happy to update further if necessary.

# if limits is a function, it expects to work in data space
self$trans$transform(self$limits(self$trans$inverse(self$range$range)))
} else if (!is.null(self$limits)) {
ifelse(!is.na(self$limits), self$limits, self$range$range)
} else {
self$range$range
Expand Down Expand Up @@ -526,8 +530,11 @@ ScaleDiscrete <- ggproto("ScaleDiscrete", Scale,
#' - A character vector giving labels (must be same length as `breaks`)
#' - A function that takes the breaks as input and returns labels
#' as output
#' @param limits A numeric vector of length two providing limits of the scale.
#' Use `NA` to refer to the existing minimum or maximum.
#' @param limits One of:
#' - A numeric vector of length two providing limits of the scale.
#' Use `NA` to refer to the existing minimum or maximum
#' - A function that accepts the existing (automatic) limits and returns
#' new limits
#' @param rescaler Used by diverging and n colour gradients
#' (i.e. [scale_colour_gradient2()], [scale_colour_gradientn()]).
#' A function used to scale the input values to the range \eqn{[0, 1]}.
Expand Down Expand Up @@ -565,7 +572,7 @@ continuous_scale <- function(aesthetics, scale_name, palette, name = waiver(),
}

trans <- as.trans(trans)
if (!is.null(limits)) {
if (!is.null(limits) && !is.function(limits)) {
limits <- trans$transform(limits)
}

Expand Down Expand Up @@ -598,7 +605,7 @@ continuous_scale <- function(aesthetics, scale_name, palette, name = waiver(),
#'
#' @export
#' @inheritParams continuous_scale
#' @param breaks One of:
#' @param breaks One of:
#' - `NULL` for no breaks
#' - `waiver()` for the default breaks computed by the
#' transformation object
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