lacking function for CIRCLE on landscape level

NAMESPACE

@@ -71,6 +71,7 @@ export(vm_c_te)
 export(vm_l_area_mn)
 export(vm_l_cai_mn)
 export(vm_l_circ_mn)
+export(vm_l_circle_mn)
 export(vm_l_coh_mn)
 export(vm_l_comp_mn)
 export(vm_l_convex_mn)

R/vm_l_circle_mn.R

@@ -0,0 +1,27 @@
+#' @title The mean value of Ratios between the patch area
+#' and the smallest circumscribing circle of patches at class level(vector data)
+#' 
+#' @description This function allows you to calculate the mean value of ratios of each class in a categorical landscape in vector data format
+#' the ratio is the patch area relative to area of the smallest circumscribing circle of the patch
+#' @param landscape the input landscape image,
+#' @param class_col the name of the class column of the input landscape
+#' @return  the returned calculated mean value of ratios of each class is in column "value",
+#' and this function returns also some important information such as level, class number and metric name.
+#' Moreover, the "id" column, although it is just NA here at class level. we need it because the output struture of metrics
+#' at class level should correspond to patch level one by one, and then it is more convinient to combine metric values at different levels and compare them.
+#' @examples
+#' vm_l_circle_mn(vector_landscape, "class")
+#' @export
+
+vm_l_circle_mn <- function(landscape){
+  circle <- vm_p_circle(landscape)
+  circle_l <- mean(circle$value)
+
+  tibble::new_tibble(list(
+    level = "landscape",
+    class = as.character(NA),
+    id = as.character(NA),
+    metric = "circle_mn",
+    value = as.double(circle_l)
+  ))
+}