diff --git a/.Rbuildignore b/.Rbuildignore
index 0c889a0..a4607f2 100644
--- a/.Rbuildignore
+++ b/.Rbuildignore
@@ -5,3 +5,4 @@
 .gitignore
 .travis.yml
 _pkgdown.yml
+codecov.yml
diff --git a/.Rproj.user/84277BCC/sources/prop/INDEX b/.Rproj.user/84277BCC/sources/prop/INDEX
index 153f2f6..4fff322 100644
--- a/.Rproj.user/84277BCC/sources/prop/INDEX
+++ b/.Rproj.user/84277BCC/sources/prop/INDEX
@@ -3,6 +3,7 @@ C%3A%2FUsers%2FZehao%2FDesktop%2FdatashadeR%2Fapp.R="D62258AD"
 C%3A%2FUsers%2FZehao%2FDesktop%2FdatashadeR%2Fnew_app.R="4D4286E2"
 C%3A%2FUsers%2FZehao%2FDesktop%2FdatashadeR%2Frasterizer%2FR%2Fplotly_rasterizer.R="9B582184"
 C%3A%2FUsers%2FZehao%2FDesktop%2FdatashadeR%2Ftime.R="3E5BAB2D"
+C%3A%2FUsers%2FZehao%2FDesktop%2Fplotly%2FdatashadeR%2Ftime.R="272E2EC2"
 C%3A%2FUsers%2FZehao%2FDesktop%2Funtitled.Rmd="4192FD99"
 C%3A%2Frsa.pub="2A39FFB6"
 ~%2FGitHub%2FDocuments.pub="C29300F9"
@@ -66,11 +67,28 @@ C%3A%2Frsa.pub="2A39FFB6"
 ~%2FGitHub%2Frasterly%2FDESCRIPTION="74BE175A"
 ~%2FGitHub%2Frasterly%2FNAMESPACE="1DD17E96"
 ~%2FGitHub%2Frasterly%2FR%2F_pkgdown.yml="59F334FE"
+~%2FGitHub%2Frasterly%2FR%2Fadd_rasterly.R="CEDCD63B"
+~%2FGitHub%2Frasterly%2FR%2Fadd_rasterly_heatmap.R="39EA1427"
+~%2FGitHub%2Frasterly%2FR%2Fget_aesthetics.R="6B789F2F"
+~%2FGitHub%2Frasterly%2FR%2FggRasterizer.R="95867414"
 ~%2FGitHub%2Frasterly%2FR%2Fplotly_rasterizer.R="95A84FE4"
 ~%2FGitHub%2Frasterly%2FR%2Fplotly_rasterly.R="18228E5F"
+~%2FGitHub%2Frasterly%2FR%2Frasterize_points.R="2E260DA6"
+~%2FGitHub%2Frasterly%2FR%2Frasterly-package.R="BFCA8213"
+~%2FGitHub%2Frasterly%2FR%2Frasterly.R="A9996F87"
+~%2FGitHub%2Frasterly%2FR%2Frasterly_build.R="7A3C86EA"
+~%2FGitHub%2Frasterly%2FR%2Freexports.R="D1B1BBF4"
 ~%2FGitHub%2Frasterly%2FR%2Futils.R="8D9EEBAB"
 ~%2FGitHub%2Frasterly%2FREADME.md="9F226BD0"
 ~%2FGitHub%2Frasterly%2F_pkgdown.yml="BAE60E1"
+~%2FGitHub%2Frasterly%2Fcodecov.yml="B207F478"
+~%2FGitHub%2Frasterly%2Fdoc%2Fintroduction.R="5E09A20A"
+~%2FGitHub%2Frasterly%2Fdoc%2Fintroduction.Rmd="E83AB2D"
+~%2FGitHub%2Frasterly%2Fdoc%2Fintroduction.html="A1AC1F18"
+~%2FGitHub%2Frasterly%2Fman%2Fadd_rasterly.Rd="BB1B2B04"
+~%2FGitHub%2Frasterly%2Fman%2Frasterly-package.Rd="4C8DB46B"
+~%2FGitHub%2Frasterly%2Fman%2Frasterly.Rd="2FDA8D7B"
+~%2FGitHub%2Frasterly%2Ftests%2Ftestthat%2Ftest_rasterizer.R="59F3C36"
 ~%2FGitHub%2Frasterly%2Ftests%2Ftestthat.R="7976063B"
 ~%2FGitHub%2Frasterly%2Fvignettes%2Fintroduction.Rmd="2F40B97A"
 ~%2FGitHub%2Frsa.pub="8898C4BE"
diff --git a/.travis.yml b/.travis.yml
index 5761a48..0f79963 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -13,6 +13,9 @@ addons:
 sudo: false
 
 language: r
+r_github_packages:
+  - r-lib/covr
+
 before_install:
   - export DISPLAY=':99.0'
   - Xvfb :99 -screen 0 1024x768x24 > /dev/null 2>&1  &
@@ -22,4 +25,7 @@ cache: packages
 
 r:
   - release
-  - devel
\ No newline at end of file
+  - devel
+
+after_success:
+ - Rscript -e 'covr::codecov()'
\ No newline at end of file
diff --git a/DESCRIPTION b/DESCRIPTION
index ccef0e6..bc069b4 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -33,8 +33,10 @@ Suggests:
     compiler,
     loon,
     purrr,
+    covr,
     testthat,
     knitr,
+    rmarkdown,
     lubridate
 LazyData: true
 RoxygenNote: 6.1.1
diff --git a/NAMESPACE b/NAMESPACE
index bb74586..6d3a244 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -7,7 +7,7 @@ S3method(as.raster,rasterizeMatrix)
 S3method(print,rasterly)
 export("%<-%")
 export("%>%")
-export(add_rasterly)
+export(add_rasterly_heatmap)
 export(aes)
 export(fire)
 export(hourColors)
@@ -20,7 +20,6 @@ export(viridis)
 import(Rcpp)
 import(methods)
 import(rlang)
-importFrom(compiler,cmpfun)
 importFrom(data.table,data.table)
 importFrom(ggplot2,aes)
 importFrom(grDevices,as.raster)
diff --git a/R/add_rasterly.R b/R/add_rasterly_heatmap.R
similarity index 69%
rename from R/add_rasterly.R
rename to R/add_rasterly_heatmap.R
index 6f3304c..35c0f57 100644
--- a/R/add_rasterly.R
+++ b/R/add_rasterly_heatmap.R
@@ -14,49 +14,50 @@
 #'
 #' @examples
 #' \dontrun{
-#'    library(rasterly)
-#'    if(requireNamespace("plotly") && requireNamespace("data.table")) {
-#'      # Load data
-#'      ridesRaw_1 <- "https://raw.githubusercontent.com/plotly/datasets/
-#'      master/uber-rides-data1.csv" %>%
-#'        data.table::fread(stringsAsFactors = FALSE)
-#'      ridesRaw_2 <- "https://raw.githubusercontent.com/plotly/datasets/
-#'      master/uber-rides-data2.csv" %>%
-#'        data.table::fread(stringsAsFactors = FALSE)
-#'      ridesRaw_3 <- "https://raw.githubusercontent.com/plotly/datasets/
-#'      master/uber-rides-data3.csv"  %>%
-#'        data.table::fread(stringsAsFactors = FALSE)
-#'      ridesDf <- list(ridesRaw_1, ridesRaw_2, ridesRaw_3) %>%
-#'        data.table::rbindlist()
+#'library(rasterly)
+#'if(requireNamespace("plotly") && requireNamespace("data.table")) {
+#'  # Load data
+#'  url1 <- "https://raw.githubusercontent.com/plotly/datasets/master/uber-rides-data1.csv"
+#'  ridesRaw_1 <-  url1 %>%
+#'    data.table::fread(stringsAsFactors = FALSE)
+#'  url2 <- "https://raw.githubusercontent.com/plotly/datasets/master/uber-rides-data2.csv"
+#'  ridesRaw_2 <-  url2 %>%
+#'    data.table::fread(stringsAsFactors = FALSE)
+#'  url3 <- "https://raw.githubusercontent.com/plotly/datasets/master/uber-rides-data3.csv"
+#'  ridesRaw_3 <-  url3 %>%
+#'    data.table::fread(stringsAsFactors = FALSE) 
+#'    
+#'  ridesDf <- list(ridesRaw_1, ridesRaw_2, ridesRaw_3) %>%
+#'    data.table::rbindlist()
 #'
-#'      #### quick start
-#'      p <- plot_ly(data = ridesDf) %>%
-#'             add_rasterly(x = ~Lat, y = ~Lon)
-#'      p
-#'      #### set artificial scaling function
-#'      zeroOneTransform <- function(z) {
-#'        minz <- min(z)
-#'        maxz <- max(z)
-#'        M <- matrix((z - minz)/(maxz - minz), nrow = dim(z)[1])
-#'        return(M)
-#'      }
-#'      plot_ly(data = ridesDf) %>%
-#'        add_rasterly(x = ~Lat,
-#'                       y = ~Lon,
-#'                       on = ~-Lat,
-#'                       reduction_func = "max",
-#'                       scaling = zeroOneTransform) %>%
-#'        plotly::layout(
-#'          xaxis = list(
-#'            title = "x"
-#'          ),
-#'          yaxis = list(
-#'            title = "y"
-#'          )
-#'        )
-#'    }
+#'  #### quick start
+#'  p <- plot_ly(data = ridesDf) %>%
+#'         add_rasterly_heatmap(x = ~Lat, y = ~Lon)
+#'  p
+#'  #### set artificial scaling function
+#'  zeroOneTransform <- function(z) {
+#'    minz <- min(z)
+#'    maxz <- max(z)
+#'    M <- matrix((z - minz)/(maxz - minz), nrow = dim(z)[1])
+#'    return(M)
+#'  }
+#'  plot_ly(data = ridesDf) %>%
+#'    add_rasterly_heatmap(x = ~Lat,
+#'                 y = ~Lon,
+#'                 on = ~-Lat,
+#'                 reduction_func = "max",
+#'                 scaling = zeroOneTransform) %>%
+#'    plotly::layout(
+#'      xaxis = list(
+#'        title = "x"
+#'      ),
+#'      yaxis = list(
+#'        title = "y"
+#'      )
+#'    )
+#'  }
 #' }
-add_rasterly <- function(p,
+add_rasterly_heatmap <- function(p,
                          x = NULL, y = NULL, z = NULL, ...,
                          data = NULL, inherit = TRUE,
                          on = NULL, size = NULL,
@@ -93,14 +94,16 @@ add_rasterly <- function(p,
       if(is.null(exp)) {
         mapping_names[i] <- NA
       } else {
-        if(rlang::is_expression(exp)) {
+        if(rlang::is_formula(exp)) {
           the_parse <-  sub("~", "", rlang::expr_text(exp)) %>%
             rlang::parse_expr()
           mapping[[i]] <- rlang::quo(!!the_parse)
         } else if(is.numeric(exp)) {
             data[[mapping_names[i]]] <- exp
             mapping[[i]] <- rlang::quo(!!rlang::parse_expr(mapping_names[i]))
-        } else stop("'on' is neither `quote` nor a numerical value.", call. = FALSE)
+        } else {
+          stop("'size' ,'on' are neither `quote` nor a numerical value.", call. = FALSE)
+        }
       }
     }
 
diff --git a/R/get_aesthetics.R b/R/get_aesthetics.R
index 1769b08..fe599f5 100644
--- a/R/get_aesthetics.R
+++ b/R/get_aesthetics.R
@@ -56,14 +56,23 @@ get_aesthetics <- function(data = NULL, mapping = aes(), variable_check = FALSE,
 
   args <- list(...)
   abs_size <- args$size
-  max_size <- if(is.null(args$max_size)) 2 else args$max_size
+  max_size <- args$max_size %||% 2
 
   if(!is.null(data$size) || !is.null(abs_size)) {
 
     if(is.null(abs_size)) {
       # standardized size
-      std <- function(size, max_size) {floor((size - min(size))/(max(size) - min(size)) * (max_size - 1))}
-      data[, size := std(data$size, max_size)]
+      std_size <- function(size, max_size) {
+        maxS <- max(size)
+        minS <- min(size)
+        if(maxS == minS) {
+          if(maxS < 1) stop("Pixel size cannot be less than one.")
+          floor(size)
+        } else {
+          floor((size - minS)/(maxS - minS) * (max_size - 1))
+        }
+      }
+      data[, size := std_size(data$size, max_size)]
     } else {
       data[, size := abs_size]
     }
diff --git a/R/ggRasterizer.R b/R/ggRasterizer.R
index b6a6758..4bf46e5 100644
--- a/R/ggRasterizer.R
+++ b/R/ggRasterizer.R
@@ -1,34 +1,36 @@
 ggRasterly <- function(data = NULL,
-                         mapping = aes(),
-                         ...,
-                         plot_width = 600, plot_height = 600,
-                         x_range = NULL, y_range = NULL,
-                         background = "white",
-                         color_map = c('lightblue','darkblue'),
-                         color_key = NULL,
-                         show_raster = TRUE,
-                         drop_data = FALSE,
-                         variable_check = FALSE) {
+                       mapping = aes(),
+                       ...,
+                       plot_width = 600, plot_height = 600,
+                       x_range = NULL, y_range = NULL,
+                       background = "white",
+                       color_map = c('lightblue','darkblue'),
+                       color_key = NULL,
+                       show_raster = TRUE,
+                       drop_data = FALSE,
+                       variable_check = FALSE) {
   
   rastObj <- rasterly(data = data,
-                        mapping = mapping,
-                        ...,
-                        plot_width = plot_width, 
-                        plot_height = plot_height,
-                        x_range = x_range, 
-                        y_range = y_range,
-                        background = background,
-                        color_map = color_map,
-                        color_key = color_key,
-                        show_raster = show_raster,
-                        drop_data = drop_data,
-                        variable_check = variable_check) %>% 
+                      mapping = mapping,
+                      ...,
+                      plot_width = plot_width, 
+                      plot_height = plot_height,
+                      x_range = x_range, 
+                      y_range = y_range,
+                      background = background,
+                      color_map = color_map,
+                      color_key = color_key,
+                      show_raster = show_raster,
+                      drop_data = drop_data,
+                      variable_check = variable_check) %>% 
     rasterize_points() %>% 
     rasterly_build()
+
+  len <- max(plot_width, plot_height)
   
   ggObj <- ggplot2::ggplot(
-    data = data.frame(x = seq(rastObj$x_range[1], rastObj$x_range[2], length.out = rastObj$plot_width),
-                      y = seq(rastObj$y_range[1], rastObj$y_range[2], length.out = rastObj$plot_height)),
+    data = data.frame(x = seq(rastObj$x_range[1], rastObj$x_range[2], length.out = len),
+                      y = seq(rastObj$y_range[1], rastObj$y_range[2], length.out = len)),
     mapping = aes(x = x, y = y)
   )
   
@@ -46,20 +48,9 @@ ggRasterly <- function(data = NULL,
                           panel_line = theme$panel.grid$color %||% "white",
                           background = rastObj$background)
   
-  
-  
   ggObj <- ggObj + 
-    ggplot2::annotation_custom(grid::rasterGrob(image), 
-                               xmin = -Inf, xmax = Inf, 
-                               ymin = -Inf, ymax = Inf) + 
-    ggplot2::theme(
-      axis.ticks = ggplot2::element_line(),
-      axis.text.x = ggplot2::element_text(),
-      axis.text.y = ggplot2::element_text(),
-      axis.title = ggplot2::element_text(),
-      axis.title.x = ggplot2::element_text(),
-      axis.title.y = ggplot2::element_text()
-    )
+    ggplot2::annotation_custom(grid::rasterGrob(image))
+  return(ggObj)
 }
 
 gg_pretty <- function(ggObj) {
@@ -70,11 +61,11 @@ gg_pretty <- function(ggObj) {
   lapply(panel_params, 
          function(panel_param) {
            list(
-             x_major = panel_param$x$breaks,
-             x_minor = panel_param$x$minor_breaks,
+             x_major = panel_param$x.major_source,
+             x_minor = panel_param$x.minor_source,
              x_range = panel_param$x.range,
-             y_major = panel_param$y$breaks,
-             y_minor = panel_param$y$minor_breaks,
+             y_major = panel_param$y.major_source,
+             y_minor = panel_param$y.minor_source,
              y_range = panel_param$y.range
            )
          })
@@ -90,7 +81,7 @@ reset_image_bg <- function(image = NULL,
                            background = "white") {
   
   if(is.null(image)) return(grid::rectGrob())
-  
+
   dimI <- dim(image)
   
   x_range <- x_range %||% c(1, dimI[2])
@@ -111,7 +102,7 @@ reset_image_bg <- function(image = NULL,
   
   image[image == background] <- panel_background
   image <- matrix(image, nrow = dimI[1])
-  
+
   for(x in x_pos) {
     column <- image[, x]
     column[column == panel_background] <- panel_line
diff --git a/R/plotly_rasterly.R b/R/plotly_rasterly.R
index 68f164b..64de225 100644
--- a/R/plotly_rasterly.R
+++ b/R/plotly_rasterly.R
@@ -1,7 +1,7 @@
 #' @title `rasterly` to `plotly`
 #' @description Display raster image via `plotly`
 #' @param rastObj A rasterly object
-#' @param as_heatmap Draw `plotly` by adding heatmap layer. See \code{add_rasterly}
+#' @param as_heatmap Draw `plotly` by adding heatmap layer. See \code{add_rasterly_heatmap}
 #' @param scaling It could be an artificial function or a scaling way ("log", "origin") 
 #' @param sizing Specifies which dimension of the image to constrain. One of "stretch" "fill", "contain"
 #' @param ... Arguments to the layout object. For documentation, 
diff --git a/R/rasterly-package.R b/R/rasterly-package.R
index def93ca..e7fed3d 100644
--- a/R/rasterly-package.R
+++ b/R/rasterly-package.R
@@ -1,40 +1,20 @@
 #' Easily and rapidly generate raster image data for large datasets using Plotly.js 
-#' @description Create a rasterly object, to which aggregation layers may be added. This function is the first step in the process
-#' of generating raster image data using the `rasterly` package.
-#' @param data Dataset to use for generating the plot. If not provided, data must be supplied in each layer of the plot.
-#' For best performance, particularly when processing large datasets, use of \link[data.table]{data.table} is recommended.
-#' @param mapping Default list of aesthetic mappings to use for plot. The same with `ggplot2` \link[ggplot2]{aes}.
-#' See details.
-#' @param ... Other arguments which will be passed through to layers.
-#' @param plot_width Integer. The width of the image to plot; must be a positive integer. A higher value indicates a higher resolution.
-#' @param plot_height Integer. The height of the image to plot; must be a positive integer. A higher value indicates a higher resolution.
-#' @param x_range Vector of type numeric. The range of `x`; it can be used to clip the image. For larger datasets, providing `x_range`
-#' may result in improved performance.
-#' @param y_range Vector of type numeric. The range of `y`; it can be used to clip the image. For larger datasets, providing `y_range`
-#' may result in improved performance.
-#' @param background Character. The background color of the image to plot.
-#' @param color_map Vector of type character. Color(s) used to draw each pixel. The `color_map` is extended by linear interpolation
-#' independently for RGB. The darkness of the mapped color depends upon the values of the aggregation matrix.
-#' @param color_key Vector of type character. The `color_key` is used for categorical variables; it is passed when the `color` aesthetic
-#' is provided.
-#' @param show_raster Logical. Should the raster be displayed?
-#' @param drop_data Logical. When working with large datasets, drops the original data once processed according to the provided
-#' `aes()` parameters, using the `remove()` function. See details for additional information.
-#' @param variable_check Logical. If `TRUE`, drops unused columns to save memory; may result in reduced performance.
+#' @description rasterly makes it easy to rapidly generate rasters in R, 
+#' even for very large datasets, with an aesthetics-based mapping syntax that 
+#' should be familiar to users of the \link{ggplot2} package. 
+#' While rasterly does not attempt to reproduce the full functionality of the 
+#' Datashader graphics pipeline system for Python, 
+#' the rasterly API has several core elements in common with that software package.
 #' 
-#' @return An environment wrapped by a list
+#' A raster may be described as a matrix of cells or pixels arranged in grid-like 
+#' fashion, in which each pixel represents a value in the source data.
+#' 
+#' When combined with the \link{plotly} package and Plotly.js, 
+#' rasterly enables analysts to generate interactive figures with 
+#' very large datasets which are responsive enough to embed into 
+#' Dash for R applications.
 #' 
 #' @note Calling `rasterly()` without providing `rasterly_...()` layers has no effect.
 #' More info can be found in \href{https://github.com/plotly/rasterly/blob/master/README.md}{README.md}
 #'
-#' @seealso \link{rasterize_points}, \link{rasterly_build}, \link{[.rasterly}, \link{[<-.rasterly}
-#' @details 
-#' \itemize{
-#'  \item{}{The rasterly package currently supports five aesthetics via `aes()`: "x", "y", "on", "color", and "size".
-#'  The "on" aesthetic specifies the variable upon which the reduction function should be applied to generate the raster data.
-#'  }
-#'  \item{}{`drop_data` can help save space, particularly when large datasets are used. However, dropping the original dataset
-#'  may result in errors when attempting to set or update `aes()` parameters within rasterly layers.
-#' }
-#' }
-#'
\ No newline at end of file
+#' @seealso \link{rasterize_points}, \link{rasterly_build}, \link{[.rasterly}, \link{[<-.rasterly}
\ No newline at end of file
diff --git a/R/rasterly.R b/R/rasterly.R
index fe68c94..740eef8 100644
--- a/R/rasterly.R
+++ b/R/rasterly.R
@@ -1,13 +1,50 @@
+#' @title rasterly
+#' @description Create a rasterly object, to which aggregation layers may be added. This function is the first step in the process
+#' of generating raster image data using the `rasterly` package.
+#' @param data Dataset to use for generating the plot. If not provided, data must be supplied in each layer of the plot.
+#' For best performance, particularly when processing large datasets, use of \link[data.table]{data.table} is recommended.
+#' @param mapping Default list of aesthetic mappings to use for plot. The same with `ggplot2` \link[ggplot2]{aes}.
+#' See details.
+#' @param ... Other arguments which will be passed through to layers.
+#' @param plot_width Integer. The width of the image to plot; must be a positive integer. A higher value indicates a higher resolution.
+#' @param plot_height Integer. The height of the image to plot; must be a positive integer. A higher value indicates a higher resolution.
+#' @param x_range Vector of type numeric. The range of `x`; it can be used to clip the image. For larger datasets, providing `x_range`
+#' may result in improved performance.
+#' @param y_range Vector of type numeric. The range of `y`; it can be used to clip the image. For larger datasets, providing `y_range`
+#' may result in improved performance.
+#' @param background Character. The background color of the image to plot.
+#' @param color_map Vector of type character. Color(s) used to draw each pixel. The `color_map` is extended by linear interpolation
+#' independently for RGB. The darkness of the mapped color depends upon the values of the aggregation matrix.
+#' @param color_key Vector of type character. The `color_key` is used for categorical variables; it is passed when the `color` aesthetic
+#' is provided.
+#' @param show_raster Logical. Should the raster be displayed?
+#' @param drop_data Logical. When working with large datasets, drops the original data once processed according to the provided
+#' `aes()` parameters, using the `remove()` function. See details for additional information.
+#' @param variable_check Logical. If `TRUE`, drops unused columns to save memory; may result in reduced performance.
+#' 
+#' @return An environment wrapped by a list
+#' 
+#' @note Calling `rasterly()` without providing `rasterly_...()` layers has no effect.
+#' More info can be found in \href{https://github.com/plotly/rasterly/blob/master/README.md}{README.md}
+#'
+#' @seealso \link{rasterize_points}, \link{rasterly_build}, \link{[.rasterly}, \link{[<-.rasterly}
+#' @details 
+#' \itemize{
+#'  \item{}{The rasterly package currently supports five aesthetics via `aes()`: "x", "y", "on", "color", and "size".
+#'  The "on" aesthetic specifies the variable upon which the reduction function should be applied to generate the raster data.
+#'  }
+#'  \item{}{`drop_data` can help save space, particularly when large datasets are used. However, dropping the original dataset
+#'  may result in errors when attempting to set or update `aes()` parameters within rasterly layers.
+#' }
+#' }
+#'
 #' @useDynLib rasterly
 #' @import Rcpp
 #' @import rlang
 #' @import methods
 #' @importFrom grDevices rgb col2rgb hcl extendrange as.raster
-#' @importFrom magrittr '%>%'
 #' @importFrom stats ecdf approx setNames na.omit
-#' @importFrom ggplot2 aes
 #' @importFrom data.table data.table
-#' @importFrom compiler cmpfun
 #' @export
 rasterly <- function(data = NULL,
                      mapping = aes(),
diff --git a/R/reexports.R b/R/reexports.R
index 9e387ec..97abc81 100644
--- a/R/reexports.R
+++ b/R/reexports.R
@@ -1,5 +1,7 @@
+#' @importFrom magrittr '%>%'
 #' @export
 magrittr::'%>%'
 
+#' @importFrom ggplot2 aes
 #' @export
 ggplot2::aes
diff --git a/README.md b/README.md
index 3be26bb..009d2dc 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,7 @@
 # rasterly <img src="https://user-images.githubusercontent.com/9809798/67056539-75d75200-f11a-11e9-9b62-2b62a349a45b.jpg" align="right" height="144" width="124.8">
 
 [![Build Status](https://travis-ci.org/z267xu/rasterly.svg?branch=master)](https://travis-ci.org/z267xu/rasterly)
+[![Codecov test coverage](https://codecov.io/gh/z267xu/rasterly/branch/master/graph/badge.svg)](https://codecov.io/gh/z267xu/rasterly?branch=master)
 
 Easily and rapidly visualize very large datasets with R and the `plotly` package.
 
@@ -82,7 +83,28 @@ Note that, "p" is a list of environments. The display info can be accessed throu
 r <- rasterly_build(p)
 str(r)
 ```
+<<<<<<< HEAD
+"r" contains image raster and other useful info (like numeric aggregation matrices) to produce image but it does **not** provide any graphs.
+
+#### Static graph
+
+* `grid`
+```
+# same with plot(p)
+p
+```
+
+#### Interactive graph
+
+* `plotly`
+```
+plot_ly(ridesDf, x = ~Lat, y = ~Lon) %>%
+ add_rasterly_heatmap()
+```
+![](man/figures/add_rasterizer.gif)
+=======
 "r" contains image raster and other useful info (like numeric aggregation matrices) required to produce the image but it does **not** provide any graphs.
+>>>>>>> 6f569b246c3e8c0547174853d5778250bf20d2aa
 
 ## Example use in an interactive web application
 
diff --git a/_pkgdown.yml b/_pkgdown.yml
index 9445a30..d88a288 100644
--- a/_pkgdown.yml
+++ b/_pkgdown.yml
@@ -15,7 +15,8 @@ reference:
   - title: Functions
     desc:  Functions for changing ggplot structures into loon
     contents:
-    - add_rasterly
+    - add_rasterly_heatmap
     - rasterly
     - rasterly_build
-    - rasterize_points
\ No newline at end of file
+    - rasterize_points
+    - is.rasterly
\ No newline at end of file
diff --git a/codecov.yml b/codecov.yml
new file mode 100644
index 0000000..8f36b6c
--- /dev/null
+++ b/codecov.yml
@@ -0,0 +1,12 @@
+comment: false
+
+coverage:
+  status:
+    project:
+      default:
+        target: auto
+        threshold: 1%
+    patch:
+      default:
+        target: auto
+        threshold: 1%
diff --git a/man/add_rasterly.Rd b/man/add_rasterly.Rd
deleted file mode 100644
index 140de80..0000000
--- a/man/add_rasterly.Rd
+++ /dev/null
@@ -1,78 +0,0 @@
-% Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/add_rasterly.R
-\name{add_rasterly}
-\alias{add_rasterly}
-\title{Add "rasterly" trace to a Plotly visualization}
-\usage{
-add_rasterly(p, x = NULL, y = NULL, z = NULL, ..., data = NULL,
-  inherit = TRUE, on = NULL, size = NULL, scaling = NULL)
-}
-\arguments{
-\item{p}{A \code{plotly} object}
-
-\item{x}{Numeric vector or expression. The x variable, to be passed on to `aes()`.}
-
-\item{y}{Numeric or expression. The y variable, to be passed on to `aes()`.}
-
-\item{z}{Numeric. A numeric matrix (optional), to be processed with `add_heatmap`.}
-
-\item{...}{Arguments (i.e., attributes) passed along to the trace type or `rasterly`.}
-
-\item{data}{A data.frame or \link[crosstalk]{SharedData} object (optional).}
-
-\item{inherit}{Logical. Inherit attributes from \link[plotly]{plotly}?}
-
-\item{on}{Numeric vector or expression. Provides the data on which to reduce, to be passed on to `aes()`.}
-
-\item{size}{Numeric vector or expression. Pixel size for each observation, to be passed on to `aes()`.}
-
-\item{scaling}{Character string or function. The scaling method to be used for the trace.}
-}
-\description{
-Add trace to a Plotly visualization.
-}
-\examples{
-\dontrun{
-   library(rasterly)
-   if(requireNamespace("plotly") && requireNamespace("data.table")) {
-     # Load data
-     ridesRaw_1 <- "https://raw.githubusercontent.com/plotly/datasets/
-     master/uber-rides-data1.csv" \%>\%
-       data.table::fread(stringsAsFactors = FALSE)
-     ridesRaw_2 <- "https://raw.githubusercontent.com/plotly/datasets/
-     master/uber-rides-data2.csv" \%>\%
-       data.table::fread(stringsAsFactors = FALSE)
-     ridesRaw_3 <- "https://raw.githubusercontent.com/plotly/datasets/
-     master/uber-rides-data3.csv"  \%>\%
-       data.table::fread(stringsAsFactors = FALSE)
-     ridesDf <- list(ridesRaw_1, ridesRaw_2, ridesRaw_3) \%>\%
-       data.table::rbindlist()
-
-     #### quick start
-     p <- plot_ly(data = ridesDf) \%>\%
-            add_rasterly(x = ~Lat, y = ~Lon)
-     p
-     #### set artificial scaling function
-     zeroOneTransform <- function(z) {
-       minz <- min(z)
-       maxz <- max(z)
-       M <- matrix((z - minz)/(maxz - minz), nrow = dim(z)[1])
-       return(M)
-     }
-     plot_ly(data = ridesDf) \%>\%
-       add_rasterly(x = ~Lat,
-                      y = ~Lon,
-                      on = ~-Lat,
-                      reduction_func = "max",
-                      scaling = zeroOneTransform) \%>\%
-       plotly::layout(
-         xaxis = list(
-           title = "x"
-         ),
-         yaxis = list(
-           title = "y"
-         )
-       )
-   }
-}
-}
diff --git a/man/add_rasterly_heatmap.Rd b/man/add_rasterly_heatmap.Rd
new file mode 100644
index 0000000..598e469
--- /dev/null
+++ b/man/add_rasterly_heatmap.Rd
@@ -0,0 +1,80 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/add_rasterly_heatmap.R
+\name{add_rasterly_heatmap}
+\alias{add_rasterly_heatmap}
+\title{Add "rasterly" trace to a Plotly visualization}
+\usage{
+add_rasterly_heatmap(p, x = NULL, y = NULL, z = NULL, ...,
+  data = NULL, inherit = TRUE, on = NULL, size = NULL,
+  scaling = NULL)
+}
+\arguments{
+\item{p}{A \code{plotly} object}
+
+\item{x}{Numeric vector or expression. The x variable, to be passed on to `aes()`.}
+
+\item{y}{Numeric or expression. The y variable, to be passed on to `aes()`.}
+
+\item{z}{Numeric. A numeric matrix (optional), to be processed with `add_heatmap`.}
+
+\item{...}{Arguments (i.e., attributes) passed along to the trace type or `rasterly`.}
+
+\item{data}{A data.frame or \link[crosstalk]{SharedData} object (optional).}
+
+\item{inherit}{Logical. Inherit attributes from \link[plotly]{plotly}?}
+
+\item{on}{Numeric vector or expression. Provides the data on which to reduce, to be passed on to `aes()`.}
+
+\item{size}{Numeric vector or expression. Pixel size for each observation, to be passed on to `aes()`.}
+
+\item{scaling}{Character string or function. The scaling method to be used for the trace.}
+}
+\description{
+Add trace to a Plotly visualization.
+}
+\examples{
+\dontrun{
+library(rasterly)
+if(requireNamespace("plotly") && requireNamespace("data.table")) {
+ # Load data
+ url1 <- "https://raw.githubusercontent.com/plotly/datasets/master/uber-rides-data1.csv"
+ ridesRaw_1 <-  url1 \%>\%
+   data.table::fread(stringsAsFactors = FALSE)
+ url2 <- "https://raw.githubusercontent.com/plotly/datasets/master/uber-rides-data2.csv"
+ ridesRaw_2 <-  url2 \%>\%
+   data.table::fread(stringsAsFactors = FALSE)
+ url3 <- "https://raw.githubusercontent.com/plotly/datasets/master/uber-rides-data3.csv"
+ ridesRaw_3 <-  url3 \%>\%
+   data.table::fread(stringsAsFactors = FALSE) 
+   
+ ridesDf <- list(ridesRaw_1, ridesRaw_2, ridesRaw_3) \%>\%
+   data.table::rbindlist()
+
+ #### quick start
+ p <- plot_ly(data = ridesDf) \%>\%
+        add_rasterly_heatmap(x = ~Lat, y = ~Lon)
+ p
+ #### set artificial scaling function
+ zeroOneTransform <- function(z) {
+   minz <- min(z)
+   maxz <- max(z)
+   M <- matrix((z - minz)/(maxz - minz), nrow = dim(z)[1])
+   return(M)
+ }
+ plot_ly(data = ridesDf) \%>\%
+   add_rasterly_heatmap(x = ~Lat,
+                y = ~Lon,
+                on = ~-Lat,
+                reduction_func = "max",
+                scaling = zeroOneTransform) \%>\%
+   plotly::layout(
+     xaxis = list(
+       title = "x"
+     ),
+     yaxis = list(
+       title = "y"
+     )
+   )
+ }
+}
+}
diff --git a/man/figures/logo.png b/man/figures/logo.png
index 6a16d16..3761ed5 100644
Binary files a/man/figures/logo.png and b/man/figures/logo.png differ
diff --git a/man/plotly.rasterly.Rd b/man/plotly.rasterly.Rd
index 411ddc9..98ee91c 100644
--- a/man/plotly.rasterly.Rd
+++ b/man/plotly.rasterly.Rd
@@ -10,7 +10,7 @@ plotly.rasterly(rastObj, as_heatmap = FALSE, scaling = NULL,
 \arguments{
 \item{rastObj}{A rasterly object}
 
-\item{as_heatmap}{Draw `plotly` by adding heatmap layer. See \code{add_rasterly}}
+\item{as_heatmap}{Draw `plotly` by adding heatmap layer. See \code{add_rasterly_heatmap}}
 
 \item{scaling}{It could be an artificial function or a scaling way ("log", "origin")}
 
diff --git a/man/rasterly-package.Rd b/man/rasterly-package.Rd
index 6ca0f37..b737c91 100644
--- a/man/rasterly-package.Rd
+++ b/man/rasterly-package.Rd
@@ -1,6 +1,5 @@
 \docType{package}
 \name{rasterly-package}
-\alias{rasterly}
 \alias{rasterly-package}
 \title{Easily and rapidly generate raster image data for large datasets using Plotly.js}
 \description{
@@ -12,86 +11,12 @@ A raster may be described as a matrix of cells or pixels arranged in grid-like f
 
 When combined with the \link{plotly} package and Plotly.js, rasterly enables analysts to generate interactive figures with very large datasets which are responsive enough to embed into Dash for R applications.
 }
-\usage{
-rasterly(data = NULL, mapping = aes(), ..., plot_width = 600,
-  plot_height = 600, x_range = NULL, y_range = NULL,
-  background = "white", color_map = c("lightblue", "darkblue"),
-  color_key = NULL, show_raster = TRUE, drop_data = FALSE,
-  variable_check = FALSE)
-}
-\arguments{
-\item{data}{Dataset to use for generating the plot. If not provided, data must be supplied in each layer of the plot.
-For best performance, particularly when processing large datasets, use of \link[data.table]{data.table} is recommended.}
-
-\item{mapping}{Default list of aesthetic mappings to use for plot. The same with `ggplot2` \link[ggplot2]{aes}.
-See details.}
-
-\item{...}{Other arguments which will be passed through to layers.}
-
-\item{plot_width}{Integer. The width of the image to plot; must be a positive integer. A higher value indicates a higher resolution.}
-
-\item{plot_height}{Integer. The height of the image to plot; must be a positive integer. A higher value indicates a higher resolution.}
-
-\item{x_range}{Vector of type numeric. The range of `x`; it can be used to clip the image. For larger datasets, providing `x_range`
-may result in improved performance.}
-
-\item{y_range}{Vector of type numeric. The range of `y`; it can be used to clip the image. For larger datasets, providing `y_range`
-may result in improved performance.}
-
-\item{background}{Character. The background color of the image to plot.}
 
-\item{color_map}{Vector of type character. Color(s) used to draw each pixel. The `color_map` is extended by linear interpolation
-independently for RGB. The darkness of the mapped color depends upon the values of the aggregation matrix.}
-
-\item{color_key}{Vector of type character. The `color_key` is used for categorical variables; it is passed when the `color` aesthetic
-is provided.}
-
-\item{show_raster}{Logical. Should the raster be displayed?}
-
-\item{drop_data}{Logical. When working with large datasets, drops the original data once processed according to the provided
-`aes()` parameters, using the `remove()` function. See details for additional information.}
-
-\item{variable_check}{Logical. If `TRUE`, drops unused columns to save memory. Use of this option may result in reduced performance.}
-}
-\value{
-An environment wrapped by a list which defines the properties of the raster data to be generated.
-}
-\description{
-Create a rasterly object, to which aggregation layers may be added. This function is the first step in the process
-of generating raster image data using the package. The `rasterly` function is not intended to be used in isolation, since aggregation layers are required for full functionality.
-}
-\details{
-\itemize{
- \item{}{The rasterly package currently supports five aesthetics via `aes()`: "x", "y", "on", "color", and "size".
- The "on" aesthetic specifies the variable upon which the reduction function should be applied to generate the raster data.
- }
- \item{}{`drop_data` can help save space, particularly when large datasets are used. However, dropping the original dataset
- may result in errors when attempting to set or update `aes()` parameters within rasterly layers.
-}
-}
-}
 \note{
 Calling `rasterly()` without providing `rasterly_...()` layers has no effect.
-More info can be found in \href{https://github.com/plotly/rasterly/blob/master/README.md}{README.md}.
-}
-\examples{
-\dontrun{
-# Load data
-ridesRaw_1 <- "https://raw.githubusercontent.com/plotly/datasets/master/uber-rides-data1.csv" %>%
-  data.table::fread(stringsAsFactors = FALSE)
-ridesRaw_2 <- "https://raw.githubusercontent.com/plotly/datasets/master/uber-rides-data2.csv" %>%
-  data.table::fread(stringsAsFactors = FALSE)
-ridesRaw_3 <- "https://raw.githubusercontent.com/plotly/datasets/master/uber-rides-data3.csv"  %>%
-  data.table::fread(stringsAsFactors = FALSE)
-ridesDf <- list(ridesRaw_1, ridesRaw_2, ridesRaw_3) %>%
-  data.table::rbindlist()
-  
-ridesDf %>%
-  rasterly(mapping = aes(x = Lat, y = Lon)) %>%
-  rasterize_points() -> p
-p  
-}
+More info can be found in \href{https://github.com/plotly/rasterly/blob/master/README.md}{README.md}
 }
+
 \seealso{
 \itemize{
   \link{rasterize_points}, \link{rasterly_build}, \link{[.rasterly}, \link{[<-.rasterly}
@@ -100,3 +25,18 @@ p
   \item Please report bugs at \url{https://github.com/plotly/rasterly/issues}
 }
 }
+
+\author{
+\strong{Maintainer}: Zehao Xu \email{z267xu@uwaterloo.ca}
+
+Authors:
+\itemize{
+  \item Zehao Xu \email{z267xu@uwaterloo.ca}
+  \item Ryan Patrick Kyle \email{ryan@plot.ly}
+}
+
+Other contributors:
+\itemize{
+  \item  Plotly Technologies [copyright holder]
+}
+}
diff --git a/src/RcppExports.o b/src/RcppExports.o
deleted file mode 100644
index d1020bd..0000000
Binary files a/src/RcppExports.o and /dev/null differ
diff --git a/tests/testthat.R b/tests/testthat.R
index 7089aff..5c3ee05 100644
--- a/tests/testthat.R
+++ b/tests/testthat.R
@@ -1,4 +1,4 @@
-
 library(testthat)
 library(rasterly)
 
+test_check("rasterly")
\ No newline at end of file
diff --git a/tests/testthat/test_rasterizer.R b/tests/testthat/test_rasterizer.R
index d1d3c43..8fb10b5 100644
--- a/tests/testthat/test_rasterizer.R
+++ b/tests/testthat/test_rasterizer.R
@@ -2,6 +2,7 @@ context("test examples")
 library(data.table)
 library(magrittr)
 library(grid)
+library(plotly)
 library(rasterly)
 
 data <- data.table::data.table(x = rnorm(1e5), y = rnorm(1e5), z = sample(1:5, 1e5, replace = TRUE))
@@ -183,4 +184,10 @@ test_that("example works", {
     rasterize_points(color_map = fire, group_by_data_table = FALSE) %>%
     rasterly_build() -> ds
   expect_equal(is.rasterly(ds), TRUE)
+  
+  # add_rasterly_heatmap
+  p <- plot_ly(data = data) %>%
+         add_rasterly_heatmap(x = ~x, y = ~y)
+  p
+  expect_equal(inherits(p, "plotly"), TRUE)
 })
diff --git a/vignettes/introduction.Rmd b/vignettes/introduction.Rmd
index 66c247e..c5cfd7f 100644
--- a/vignettes/introduction.Rmd
+++ b/vignettes/introduction.Rmd
@@ -123,17 +123,17 @@ It contains:
 
 #### `plotly` graphics
 
-  + `add_rasterly()`: Layers are added to Plotly objects via `add_trace(...)`; `rasterly` provides the `add_rasterly()` function which also leverages `add_heatmap()` to generate single channel heatmap overlays for Plotly figures. Multi-channel heatmaps are not currently supported; this feature will be available in an upcoming release.
+  + `add_rasterly_heatmap()`: Layers are added to Plotly objects via `add_trace(...)`; `rasterly` provides the `add_rasterly_heatmap()` function which also leverages `add_heatmap()` to generate single channel heatmap overlays for Plotly figures. Multi-channel heatmaps are not currently supported; this feature will be available in an upcoming release.
     
-    ```{r add_rasterly, fig.width = 4, fig.height = 3}
+    ```{r add_rasterly_heatmap, fig.width = 4, fig.height = 3}
     plotly::plot_ly(ridesDf, x = ~Lat, y = ~Lon) %>%
-      add_rasterly() %>% 
+      add_rasterly_heatmap() %>% 
       layout(
         title = "Uber drives",
-        x <- list(
+        x = list(
           title = "Lat"
         ),
-        y <- list(
+        y = list(
           title = "Lon"
         )
       )