add fun areaCaculator

DESCRIPTION

@@ -15,10 +15,12 @@ Encoding: UTF-8
 LazyData: true
 Imports: 
     geojsonsf,
+    geosphere,
     htmltools,
     htmlwidgets,
     leaflet,
     leaflet.extras,
+    purrr,
     Rcpp,
     sf,
     stringr

NAMESPACE

@@ -3,6 +3,7 @@
 export(addCityShape)
 export(addProvinceShape)
 export(addTilesAmap)
+export(areaCalculator)
 export(convertCoordinates)
 import(sf)
 importFrom(Rcpp,sourceCpp)

R/areaCalculator.R

@@ -0,0 +1,91 @@
+#' Calculate the area of a polygon defined by latitude and longitude points
+#'
+#' This function takes in latitude and longitude vectors and calculates the area of the polygon
+#' defined by those points. It can handle different coordinate systems such as WGS-84, GCJ-02, and BD-09.
+#'
+#' @param longitude A numeric vector of longitude points.
+#' @param latitude A numeric vector of latitude points.
+#' @param coordinate A string indicating the coordinate system of the input points, can be "WGS-84",
+#'        "GCJ-02", or "BD-09". Default is "WGS-84".
+#' @param chull A logical value indicating whether to use the convex hull of the points. Default is TRUE.
+#'
+#' @return A numeric value representing the area of the polygon in square meters.
+#' @export
+#'
+#' @examples
+#' area <- areaCalculator(
+#'   latitude = c(31.0, 31.1, 31.2),
+#'   longitude = c(121.0, 121.1, 121.2), coordinate = "WGS-84"
+#' )
+areaCalculator <- function(longitude,
+                           latitude,
+                           coordinate = "WGS-84",
+                           chull = TRUE) {
+  # Check if latitude and longitude lengths match
+  if (length(latitude) != length(longitude)) {
+    stop("Latitude and longitude vectors must have the same length.")
+  }
+  if (!coordinate %in% c("WGS-84", "GCJ-02", "BD-09")) {
+    stop("coordinate must be one of WGS-84, GCJ-02, and BD-09")
+  }
+
+  # Create a data frame with the input coordinates
+  data <- data.frame(longitude = longitude, latitude = latitude)
+
+  # Convert coordinates to WGS-84 if necessary
+  if (coordinate == "GCJ-02") {
+    data$latitude <- purrr::map2(
+      .x = latitude,
+      .y = longitude,
+      \(x, y)convertCoordinates(
+        latitude = x,
+        longitude = y,
+        from = "GCJ-02",
+        to = "WGS-84"
+      )[1]
+    )
+    data$longitude <- purrr::map2(
+      .x = latitude,
+      .y = longitude,
+      \(x, y)convertCoordinates(
+        latitude = x,
+        longitude = y,
+        from = "GCJ-02",
+        to = "WGS-84"
+      )[2]
+    )
+  } else if (coordinate == "BD-09") {
+    data$latitude <- purrr::map2(
+      .x = latitude,
+      .y = longitude,
+      \(x, y)convertCoordinates(
+        latitude = x,
+        longitude = y,
+        from = "BD-09",
+        to = "WGS-84"
+      )[1]
+    )
+    data$longitude <- purrr::map2(
+      .x = latitude,
+      .y = longitude,
+      \(x, y)convertCoordinates(
+        latitude = x,
+        longitude = y,
+        from = "BD-09",
+        to = "WGS-84"
+      )[2]
+    )
+  }
+
+
+  # Filter the data to include only the convex hull points if chull is TRUE
+  if (chull) {
+    data <- data[chull(data$longitude, data$latitude), ]
+  }
+
+
+  # Calculate the area of the polygon
+  area <- geosphere::areaPolygon(data)
+
+  return(area)
+}