diff --git a/R/compute_viewshed.R b/R/compute_viewshed.R
index ceea8a0..5b9c632 100644
--- a/R/compute_viewshed.R
+++ b/R/compute_viewshed.R
@@ -12,7 +12,7 @@
 #' @param offset_height numeric, setting the height of positions that a given
 #' viewpoint will look at. (defaut is 0)
 #' @param r Numeric (optional), setting the radius for viewshed analysis.
-#' (it is defaulted as NULL)
+#' (The default is 1000m/3281ft)
 #' @param parallel Logical, (default is FALSE) indicating if parallel computing
 #' should be used to compute viewsheds of multiview points. When it is TRUE,
 #' arguements 'raster' and 'plot' are ignored
diff --git a/man/compute_viewshed.Rd b/man/compute_viewshed.Rd
index fad7c81..073668b 100644
--- a/man/compute_viewshed.Rd
+++ b/man/compute_viewshed.Rd
@@ -29,7 +29,7 @@ or a matrix including several viewpoints with x,y coordinates}
 viewpoint will look at. (defaut is 0)}
 
 \item{r}{Numeric (optional), setting the radius for viewshed analysis.
-(it is defaulted as NULL)}
+(The default is 1000m/3281ft)}
 
 \item{parallel}{Logical, (default is FALSE) indicating if parallel computing
 should be used to compute viewsheds of multiview points. When it is TRUE,
diff --git a/src/viewscape.so b/src/viewscape.so
index a63a040..c2ea07e 100755
Binary files a/src/viewscape.so and b/src/viewscape.so differ
diff --git a/src/visibleLabel.cpp b/src/visibleLabel.cpp
index 2f7806d..d941e79 100644
--- a/src/visibleLabel.cpp
+++ b/src/visibleLabel.cpp
@@ -13,20 +13,21 @@ Rcpp::IntegerMatrix visibleLabel(
     const double h,
     const int max_dis) {
 
-  Rcpp::NumericVector zl;
-  Rcpp::NumericVector xl;
-  Rcpp::NumericVector yl;
+  // Rcpp::NumericVector zl;
+  // Rcpp::NumericVector xl;
+  // Rcpp::NumericVector yl;
   const int rows = dsm.rows();
   const int cols = dsm.cols();
   int steps;
   Rcpp::IntegerMatrix visible(rows, cols);
+  Rcpp::NumericVector sequence(max_dis), xl(max_dis), yl(max_dis), zl(max_dis);
 
   for (int i = 0; i < rows; i++) {
      for (int j = 0; j < cols; j++) {
        steps = sqrt((viewpoint[0]-j)*(viewpoint[0]-j) + (viewpoint[1]-i)*(viewpoint[1]-i));
        const double z = dsm(i,j) + h;
        if (steps <= max_dis) {
-         Rcpp::NumericVector sequence(steps);
+         // Rcpp::NumericVector sequence(steps);
          std::iota(sequence.begin(), sequence.end(), 1);
          xl = viewpoint[0] + sequence * (j-viewpoint[0])/steps;
          yl = viewpoint[1] + sequence * (i-viewpoint[1])/steps;
diff --git a/src/visibleLabel.o b/src/visibleLabel.o
index 85b6eda..a883ac4 100644
Binary files a/src/visibleLabel.o and b/src/visibleLabel.o differ