Provide more examples in calculate_indices()

R/calculate_indices.R

@@ -51,16 +51,38 @@
 #'   names_suffix = "sentinel1"
 #' )
 #'
-#' # Formulas aren't able to access most R functions or operators:
+#' # Formulas aren't able to access most R functions or operators,
+#' # in order to try and keep formulas from doing something bad:
 #' example_indices <- filter_platforms(platforms = "Sentinel-1 (Dual Polarisation VV-VH)")[1, ]
 #' example_indices$formula <- 'system("echo something bad")'
+#' # So this will error:
 #' try(
 #'   calculate_indices(
 #'     system.file("rasters/example_sentinel1.tif", package = "rsi"),
 #'     example_indices,
 #'     tempfile(fileext = ".tif")
 #'   )
 #' )
+#' 
+#' # Because of this, formulas which try to use most R functions
+#' # will wind up erroring as well:
+#' example_indices$formula <- "pmax(VH, VV)"
+#' try(
+#'   calculate_indices(
+#'     system.file("rasters/example_sentinel1.tif", package = "rsi"),
+#'     example_indices,
+#'     tempfile(fileext = ".tif")
+#'   )
+#' )
+#' 
+#' # To fix this, pass the objects you want to use to `extra_objects`
+#' calculate_indices(
+#'   system.file("rasters/example_sentinel1.tif", package = "rsi"),
+#'   example_indices,
+#'   tempfile(fileext = ".tif"),
+#'   extra_objects = list(pmax = pmax)
+#' ) |>
+#'   suppressWarnings(classes = "rsi_extra_objects")
 #'
 #' @export
 calculate_indices <- function(raster,