Don't install interp (#4806)

It's only needed for a small example and it uses RcppEigen which is having install problems on one version of R.

Author: hadley

.github/workflows/R-CMD-check.yaml

@@ -66,7 +66,6 @@ jobs:
             mapproj=?ignore-before-r=3.5.0,
             multcomp=?ignore-before-r=3.5.0,
             quantreg=?ignore-before-r=3.5.0,
-            interp=?ignore-before-r=3.5.0
           needs: check
 
       - uses: r-lib/actions/check-r-package@v2

DESCRIPTION

@@ -51,7 +51,6 @@ Suggests:
     ggplot2movies,
     hexbin,
     Hmisc,
-    interp,
     knitr,
     lattice,
     mapproj,

R/geom-contour.r

@@ -1,16 +1,15 @@
 #' 2D contours of a 3D surface
 #'
+#' @description
 #' ggplot2 can not draw true 3D surfaces, but you can use `geom_contour()`,
-#' `geom_contour_filled()`, and [geom_tile()] to visualise 3D surfaces in 2D. To
-#' specify a valid surface, the data must contain `x`, `y`, and `z` coordinates,
-#' and each unique combination of `x` and `y` can appear at most once.
-#' Contouring requires that the points can be rearranged so that the `z` values
-#' form a matrix, with rows corresponding to unique `x` values, and columns
-#' corresponding to unique `y` values. Missing entries are allowed, but contouring
-#' will only be done on cells of the grid with all four `z` values present. If
-#' your data is irregular, you can interpolate to a grid before visualising
-#' using the [interp::interp()] function from the `interp` package
-#' (or one of the interpolating functions from the `akima` package.)
+#' `geom_contour_filled()`, and [geom_tile()] to visualise 3D surfaces in 2D.
+#'
+#' These functions require regular data, where the `x` and `y` coordinates
+#' form an equally spaced grid, and each combination of `x` and `y` appears
+#' once. Missing values of `z` are allowed, but contouring will only work for
+#' grid points where all four corners are non-missing. If you have irregular
+#' data, you'll need to first interpolate on to a grid before visualising,
+#' using [interp::interp()], [akima::bilinear()], or similar.
 #'
 #' @eval rd_aesthetics("geom", "contour")
 #' @eval rd_aesthetics("geom", "contour_filled")
@@ -56,22 +55,6 @@
 #' v + geom_contour(colour = "red")
 #' v + geom_raster(aes(fill = density)) +
 #'   geom_contour(colour = "white")
-#'
-#' # Irregular data
-#' if (requireNamespace("interp")) {
-#'   # Use a dataset from the interp package
-#'   data(franke, package = "interp")
-#'   origdata <- as.data.frame(interp::franke.data(1, 1, franke))
-#'   grid <- with(origdata, interp::interp(x, y, z))
-#'   griddf <- subset(data.frame(x = rep(grid$x, nrow(grid$z)),
-#'                               y = rep(grid$y, each = ncol(grid$z)),
-#'                               z = as.numeric(grid$z)),
-#'                    !is.na(z))
-#'   ggplot(griddf, aes(x, y, z = z)) +
-#'     geom_contour_filled() +
-#'     geom_point(data = origdata)
-#' } else
-#'   message("Irregular data requires the 'interp' package")
 #' }
 geom_contour <- function(mapping = NULL, data = NULL,
                          stat = "contour", position = "identity",