create scale_id_continuous

DESCRIPTION

@@ -10,7 +10,9 @@ Encoding: UTF-8
 Roxygen: list(markdown = TRUE)
 RoxygenNote: 7.3.1
 Imports: 
-    grDevices
+    ggplot2,
+    grDevices,
+    scales
 Suggests: 
     testthat (>= 3.0.0)
 Config/testthat/edition: 3

NAMESPACE

@@ -6,6 +6,7 @@ export(iddu)
 export(idem)
 export(idpal)
 export(idpalette)
+export(scale_id_continuous)
 importFrom(grDevices,rgb)
 importFrom(graphics,image)
 importFrom(graphics,par)

R/scale_id_continuous.R

@@ -0,0 +1,50 @@
+#' @title scale ID continuous
+#' @description Convenience wrapper to `ggplot2::continuous_scale` to allow use of
+#' `idpalette` or any arbitrary set of colours to be used as a `ggplot2` fill
+#' or colour scale
+#'
+#' @param cols `character`. A vector of colours
+#' @param aesthetics Scale aesthetic.
+#' @param na.value Garn - whaddaya want in the `NA`s?
+#'
+#' @return A `ggproto` object of class `Scale` and `ScaleContinuous`
+#' @export
+#'
+#' @examples
+#'
+#' library(ggplot2)
+#'
+#' ggplot(mtcars) +
+#'   geom_point(
+#'     aes(
+#'       x = disp,
+#'       y = hp,
+#'       colour = qsec
+#'     ),
+#'     size = 5
+#'   ) +
+#'   scale_id_continuous(
+#'     cols = iddu(),
+#'     aesthetics = "colour"
+#'   )
+#'
+scale_id_continuous <- function(
+  cols,
+  aesthetics = c("fill", "colour"),
+  na.value = "transparent"
+){
+
+  aesthetics <- match.arg(aesthetics)
+
+  ggplot2::continuous_scale(
+    aesthetics = aesthetics,
+    palette = scales::pal_gradient_n(
+      colours = cols,
+      values = NULL,
+      space = "Lab"
+    ),
+    na.value = na.value,
+    guide = "colourbar",
+  )
+
+}

README.Rmd

@@ -153,7 +153,7 @@ ggplot(mpg) +
 
 Works with `terra` plotting:
 
-```{r, fig.height=3}
+```{r, fig.height=4}
 library(sdmtools)
 library(terra)
 
@@ -172,3 +172,24 @@ plot(
 )
 ```
 
+Sometimes `ggplot2` won't play nicely being fed a vector of values for
+continuous scales, so `scale_id_continuous` allows `idpalette` or any arbitrary
+vector of colours to be used:
+```{r, fig.height= 4}
+library(ggplot2)
+
+ggplot(mtcars) +
+ geom_point(
+   aes(
+     x = disp,
+     y = hp,
+     colour = qsec
+   ),
+   size = 5
+ ) +
+ scale_id_continuous(
+   cols = iddu(),
+   aesthetics = "colour"
+ )
+```
+

README.md

@@ -194,3 +194,27 @@ plot(
 ```
 
 <img src="man/figures/README-unnamed-chunk-16-1.png" width="100%" />
+
+Sometimes `ggplot2` won’t play nicely being fed a vector of values for
+continuous scales, so `scale_id_continuous` allows `idpalette` or any
+arbitrary vector of colours to be used:
+
+``` r
+library(ggplot2)
+
+ggplot(mtcars) +
+ geom_point(
+   aes(
+     x = disp,
+     y = hp,
+     colour = qsec
+   ),
+   size = 5
+ ) +
+ scale_id_continuous(
+   cols = iddu(),
+   aesthetics = "colour"
+ )
+```
+
+<img src="man/figures/README-unnamed-chunk-17-1.png" width="100%" />