export recommended slope color palette and break thresholds #34

NAMESPACE

@@ -8,6 +8,8 @@ export(plot_dz)
 export(plot_slope)
 export(route_to_segments)
 export(sequential_dist)
+export(slope_breaks)
+export(slope_colors)
 export(slope_distance)
 export(slope_distance_mean)
 export(slope_distance_weighted)

R/palette.R

@@ -1,5 +1,45 @@
 # R/palette.R
 
+#' Recommended slope colours (dark green to dark red)
+#'
+#' A character vector of twelve hex colours for use with \code{\link{slope_breaks}}
+#' and \code{\link{plot_slope}}. Colours run from dark green (flat) through amber
+#' to dark red (steep), covering both downhill (negative) and uphill (positive)
+#' slope directions — six colours per direction.
+#'
+#' @format A character vector of length 12.
+#' @seealso \code{\link{slope_breaks}}, \code{\link{slopes_palette}}
+#' @examples
+#' slope_colors
+#' \donttest{
+#' route_xyz <- elevation_add(lisbon_route, dem = dem_lisbon())
+#' plot_slope(route_xyz, pal = slope_colors, brks = slope_breaks)
+#' }
+#' @export
+slope_colors <- c(
+  "#730000", "#A80000", "#E60000", "#FFAA00", "#70A800", "#267300",  # downhill
+  "#267300", "#70A800", "#FFAA00", "#E60000", "#A80000", "#730000"   # uphill
+)
+
+#' Recommended slope break thresholds
+#'
+#' A numeric vector of six positive break points in **percentage units**
+#' (e.g. 5 = 5\%), without \code{0} or \code{Inf}.
+#' \code{\link{plot_slope}} uses these to build a symmetric set of 12 intervals
+#' (downhill and uphill), matched to the 12 colours in \code{\link{slope_colors}}.
+#'
+#' @format A numeric vector of length 6.
+#' @seealso \code{\link{slope_colors}}, \code{\link{slopes_palette}}
+#' @examples
+#' slope_breaks
+#' \donttest{
+#' route_xyz <- elevation_add(lisbon_route, dem = dem_lisbon())
+#' plot_slope(route_xyz, pal = slope_colors, brks = slope_breaks)
+#' }
+#' @export
+slope_breaks <- c(3, 5, 8, 10, 20, 100)
+
+
 #' Get color palette for slopes visualization
 #'
 #' Returns a color palette suitable for visualizing slope data, with options

vignettes/slopes.Rmd

@@ -132,11 +132,9 @@ slope
 You can visualize the elevation profile of a 3D linestring using `plot_slope()`:
 
 ```{r}
-# ensure a palette and breaks exist
-brks <- c(3, 6, 10, 20, 40, 100)
-pal <- slopes_palette(length(brks) - 1)
+# Use the recommended green-to-red palette and matching break thresholds
 
-plot_slope(sf_linestring_xyz_local, pal = pal, brks = brks)
+plot_slope(sf_linestring_xyz_local, pal = slope_colors, brks = slope_breaks)
 ```
 
 ## Working with segments
@@ -157,7 +155,8 @@ summary(lisbon_route_segments_xyz$slope)
 
 ```{r}
 plot(st_geometry(lisbon_route_segments_xyz),
-  col = heat.colors(length(lisbon_route_segments_xyz$slope))[rank(lisbon_route_segments_xyz$slope)],
+  col = slope_colors[7:12][cut(abs(lisbon_route_segments_xyz$slope) * 100,
+    breaks = slope_breaks, labels = FALSE, include.lowest = TRUE)],
   lwd = 3, main = "Slope by vertex segments"
 )
 ```
@@ -176,7 +175,8 @@ summary(lisbon_route_100m_xyz$slope)
 
 ```{r}
 plot(st_geometry(lisbon_route_100m_xyz),
-  col = heat.colors(length(lisbon_route_100m_xyz$slope))[rank(lisbon_route_100m_xyz$slope)],
+  col = slope_colors[7:12][cut(abs(lisbon_route_100m_xyz$slope) * 100,
+    breaks = slope_breaks, labels = FALSE, include.lowest = TRUE)],
   lwd = 3, main = "Slope by 100 m segments"
 )
 ```