add text method

NAMESPACE

@@ -357,6 +357,7 @@ S3method(st_zm,sfg)
 S3method(str,sfc)
 S3method(summary,sfc)
 S3method(t,sgbp)
+S3method(text,sf)
 S3method(transform,sf)
 S3method(vec_cast.sfc,default)
 S3method(vec_cast.sfc,sfc)

R/plot.R

@@ -700,6 +700,25 @@ sf.colors = function (n = 10, cutoff.tails = c(0.35, 0.2), alpha = 1, categorica
 	}
 }
 
+# Add text to an existing graphic
+#
+#' @param labels character, text to draw (one per row of input)
+#' @param of_largest_polygon logical, passed on to \code{st_centroid}
+#' @name plot
+#' @export
+#' @details Adds text to an existing graphic. Text is placed at the centroid of 
+#'   each feature in \code{x}.  Provide POINT features for full control of placement.
+#' @examples
+#' text(nc, labels = substring(nc$NAME,1,1))
+text.sf = function(x, labels = row.names, ..., of_largest_polygon = FALSE){
+  x = st_geometry(x) 
+  x = st_centroid(x, of_largest_polygon = FALSE)
+  xy = st_coordinates(x)
+  text(xy[,1], xy[,2], labels = labels, ...)
+}
+
+
+
 # get the aspect ratio of a bounding box, for geodetic coords true scale at mid latitude:
 get_asp = function(bb) {
 	asp = diff(bb[c(2,4)])/diff(bb[c(1,3)])