added ability to accept different spatial objects as background maps …

…in make_frames. Also added code to convert spatial object if not sf class. Adjusted documentation to reflrect these added features.

R/vis-make_frames.r

@@ -53,8 +53,8 @@
 #' @param preview write first frame only.  Useful for checking output before
 #'  processing large number of frames.  Default `preview = FALSE`
 #'
-#' @param bg_map A sf points, lines, or polygons object.  Spatial `sp` objects
-#'  will be converted to `sf`
+#' @param bg_map A sf points, lines, or polygons object.  Spatial `sp` or `terra` objects
+#'  will be converted to `sf`.  Coordinate system of map must be latitude/longitude (WGS 84). 
 #'
 #' @param show_progress Logical. Progress bar and status messages will be shown
 #'  if TRUE (default) and not shown if FALSE.
@@ -397,20 +397,28 @@ make_frames <- function(proc_obj, recs = NULL, out_dir = getwd(),
   } else {
     background <- bg_map
 
-    if (inherits(map, "Spatial")) {
-      map <- sf::st_as_sf(map)
+    # convert to sf if sp::Spatial object
+    if (inherits(background, "Spatial")) {
+      background <- sf::st_as_sf(background)
       message("Converted sp object to sf")
     }
 
-    # if not equal to default or NULL, then set to extent of bg_map
-    if (is.null(background_ylim) | all(background_ylim == c(41.3, 49.0))) {
-      background_ylim <-
-        as.numeric(st_bbox(bg_map)[c("xmin", "xmax")])
+    # convert to sf if map is terra::SpatVector object
+    if(inherits(background, "SpatVector")){
+      background <- sf::st_as_sf(background)
+      message("Converted terra object to sf")
     }
-    if (is.null(background_xlim) | all(background_xlim == c(-92.45, -75.87))) {
-      background_xlim <-
-        as.numeric(st_bbox(bg_map)[c("ymin", "ymax")])
+
+    # convert to WGS 84 (EPSG 4326)
+    if(st_crs(background)$epsg != 4326){
+      background <- sf::st_transform(background, 4326)
+      message("Converted background to long/lat (epsg: 4326) CRS")
     }
+
+    # if x and y limits are equal to default, then set limits to extent of bg_map
+    # if x and y limits are not equal to default, then leave as specified in input arguments.
+    if(missing(background_ylim) | all(background_ylim == c(41.3, 49.0))) background_ylim <- as.numeric(st_bbox(bg_map)[c("ymin", "ymax")])
+    if(missing(background_xlim) | all(background_xlim == c(-92.45, -75.87))) background_xlim <- as.numeric(st_bbox(bg_map)[c("xmin", "xmax")])
   }
 
   # turn off interpolated points if show_interpolated = FALSE