diff --git a/NAMESPACE b/NAMESPACE
index c4e790f..a595392 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -27,15 +27,20 @@ export(DetMiss)
 export(PopMiss)
 export(dataPlot)
 export(modelPlot)
+export(resiPlot)
 export(tree2data)
 importFrom(data.table,":=")
 importFrom(data.table,as.data.table)
+importFrom(data.table,data.table)
 importFrom(data.table,setkey)
 importFrom(ggplot2,aes)
 importFrom(ggplot2,element_text)
 importFrom(ggplot2,ggplot)
 importFrom(googleVis,gvisComboChart)
+importFrom(grid,grid.newpage)
+importFrom(grid,pushViewport)
 importFrom(grid,unit.pmax)
+importFrom(grid,viewport)
 importFrom(gridExtra,grid.arrange)
 importFrom(reshape2,melt)
 importFrom(scales,date_format)
diff --git a/R/DataSummary.R b/R/DataSummary.R
index 5aae232..0cf61c1 100644
--- a/R/DataSummary.R
+++ b/R/DataSummary.R
@@ -9,7 +9,7 @@
 #' @details This function provides a data summary including min, max, number of unique values and number if missing values.
 #' The min and max will ignore missing value in the data.  The input should be a `data.frame`.
 #' @author Sixiang Hu
-#' @importFrom data.table as.data.table :=
+#' @importFrom data.table data.table :=
 #' @export DataSummary
 #' @examples
 #' DataSummary(cars)
@@ -34,7 +34,7 @@ DataSummary.data.frame <- function(data,wt=NULL,sparkline=FALSE){
   dsMean    <- sapply(data,function(x){
     if(is.numeric(x) || is.integer(x)) as.character(round(weighted.mean(x,weight,na.rm = TRUE),6))
     else {
-      x.dt<-data.table(x,weight)
+      x.dt<-data.table::data.table(x,weight)
       dsTemp <- as.character(x.dt[,sum(weight),by=x][order(-V1)][1,list(x)])
       if(is.null(dsTemp) || is.na(dsTemp)) as.character(x.dt[,sum(weight),by=x][order(-V1)][2,list(x)])
       else dsTemp
@@ -44,7 +44,7 @@ DataSummary.data.frame <- function(data,wt=NULL,sparkline=FALSE){
   dsMax    <- sapply(data,function(x){
     if(is.numeric(x) || is.integer(x)) as.character(round(max(x,na.rm = TRUE),6))
     else {
-      x.dt<-data.table(x,weight)
+      x.dt<-data.table::data.table(x,weight)
       dsTemp <- as.character(x.dt[,sum(weight),by=x][order(-V1)][1,list(x)])
       if(is.null(dsTemp) || is.na(dsTemp)) as.character(x.dt[,sum(weight),by=x][order(-V1)][2,list(x)])
       else dsTemp
@@ -54,7 +54,7 @@ DataSummary.data.frame <- function(data,wt=NULL,sparkline=FALSE){
   dsMin    <- sapply(data,function(x){
     if(is.numeric(x) || is.integer(x)) as.character(round(min(x,na.rm = TRUE),6))
     else {
-      x.dt<-data.table(x,weight)
+      x.dt<-data.table::data.table(x,weight)
       dsTemp <- as.character(x.dt[,sum(weight),by=x][order(V1)][1,list(x)])
       if(is.null(dsTemp) || is.na(dsTemp)) as.character(x.dt[,sum(weight),by=x][order(V1)][2,list(x)])
       else dsTemp
@@ -63,7 +63,7 @@ DataSummary.data.frame <- function(data,wt=NULL,sparkline=FALSE){
   
   if (sparkline) {
     dsStr <- sapply(data,function(x) {
-      freq <- data.table(x)[,.N,by=x][order(x)][,f:=N/sum(N)]
+      freq <- data.table::data.table(x)[,.N,by=x][order(x)][,f:=N/sum(N)]
       if (dim(freq)[1]>=100) return("More than 100 levels")
       else return(paste0(round(freq[,f],3),collapse= ","))
     })
@@ -104,7 +104,7 @@ DataSummary.data.table <- function(data,wt=NULL,sparkline=FALSE){
   dsMean    <- data[,sapply(.SD,function(x){
     if(is.numeric(x) || is.integer(x)) as.character(round(weighted.mean(x,weight,na.rm = TRUE),6))
     else {
-      x.dt<- data.table(x,weight)
+      x.dt<- data.table::data.table(x,weight)
       dsTemp <- as.character(x.dt[,sum(weight),by=x][order(-V1)][1,list(x)])
       if(is.null(dsTemp) || is.na(dsTemp)) as.character(x.dt[,sum(weight),by=x][order(-V1)][2,list(x)])
       else dsTemp
@@ -114,7 +114,7 @@ DataSummary.data.table <- function(data,wt=NULL,sparkline=FALSE){
   dsMax    <- data[,sapply(.SD,function(x){
     if(is.numeric(x) || is.integer(x)) as.character(round(max(x,na.rm = TRUE),6))
     else {
-      x.dt<-data.table(x,weight)
+      x.dt<-data.table::data.table(x,weight)
       dsTemp <- as.character(x.dt[,sum(weight),by=x][order(-V1)][1,list(x)])
       if(is.null(dsTemp) || is.na(dsTemp)) as.character(x.dt[,sum(weight),by=x][order(-V1)][2,list(x)])
       else dsTemp
@@ -124,7 +124,7 @@ DataSummary.data.table <- function(data,wt=NULL,sparkline=FALSE){
   dsMin    <- data[,sapply(data,function(x){
     if(is.numeric(x) || is.integer(x)) as.character(round(min(x,na.rm = TRUE),6))
     else {
-      x.dt<-data.table(x,weight)
+      x.dt<-data.table::data.table(x,weight)
       dsTemp <- as.character(x.dt[,sum(weight),by=x][order(V1)][1,list(x)])
       if(is.null(dsTemp) || is.na(dsTemp)) as.character(x.dt[,sum(weight),by=x][order(V1)][2,list(x)])
       else dsTemp
@@ -133,7 +133,7 @@ DataSummary.data.table <- function(data,wt=NULL,sparkline=FALSE){
   
   if (sparkline) {
     dsStr <- data[,sapply(data,function(x) {
-      freq <- data.table(x)[,.N,by=x][order(x)][,f:=N/sum(N)]
+      freq <- data.table::data.table(x)[,.N,by=x][order(x)][,f:=N/sum(N)]
       if (dim(freq)[1]>=100) return("More than 100 levels")
       else return(paste0(round(freq[,f],3),collapse= ","))
     })]
diff --git a/R/PopMiss.r b/R/PopMiss.r
index ffbaff7..81bce0a 100644
--- a/R/PopMiss.r
+++ b/R/PopMiss.r
@@ -18,22 +18,12 @@ PopMiss <- function(data,na.treatment=c("mean.or.mode","delete","replace"),repla
 }
 
 #' @export
-PopMiss.factor<-function(data,na.treatment,replace=NULL){
-  num_miss <- length(which(is.na(data)))
-  if(isTRUE(na.treatment=="delete")) {
-    return(na.omit(data))
-  }
-  else if(isTRUE(na.treatment=="mean.or.mode")){
-    replace <- names(table(data))[order(table(data),decreasing=TRUE)[1]]
-  }
-  
-  if (is.null(replace)) stop("NULL value used for populating NAs. Chosen \"replace\" method, but didn't provide a value for replace parameter?")
-  data[is.na(data)] <- replace
-  return(data)
+PopMiss.factor<-function(data,na.treatment,replace){
+  PopMiss.character(data,na.treatment,replace)
 }
 
 #' @export
-PopMiss.character<-function(data,na.treatment,replace=NULL){
+PopMiss.character<-function(data,na.treatment,replace){
   num_miss <- sum(is.na(data))
   if(isTRUE(na.treatment=="delete")) {
     return(data[!is.na(data)])
@@ -48,7 +38,7 @@ PopMiss.character<-function(data,na.treatment,replace=NULL){
 }
 
 #' @export
-PopMiss.integer<-function(data,na.treatment,replace=NULL){
+PopMiss.integer<-function(data,na.treatment,replace){
   num_miss <- length(which(is.na(data)))
   if(isTRUE(na.treatment=="delete")) {
     return(na.omit(data))
@@ -62,7 +52,7 @@ PopMiss.integer<-function(data,na.treatment,replace=NULL){
 }
 
 #' @export
-PopMiss.numeric<-function(data,na.treatment,replace=NULL){
+PopMiss.numeric<-function(data,na.treatment,replace){
   num_miss <- length(which(is.na(data)))
   if(isTRUE(na.treatment=="delete")) {
     cat(paste(num_miss," rows have been delete.\n\n"))
@@ -79,7 +69,7 @@ PopMiss.numeric<-function(data,na.treatment,replace=NULL){
 }
 
 #' @export
-PopMiss.data.frame<-function(data,na.treatment,replace=NULL){
+PopMiss.data.frame<-function(data,na.treatment,replace){
   num_miss <- which(sapply(data,function(x) any(is.na(x))))
   if(isTRUE(na.treatment=="delete")) {
     return(na.omit(data))
@@ -111,7 +101,7 @@ PopMiss.data.frame<-function(data,na.treatment,replace=NULL){
 }
 
 #' @export
-PopMiss.data.table <-function(data,na.treatment,replace=NULL){
+PopMiss.data.table <-function(data,na.treatment,replace){
   num_miss <- which(data[,sapply(.SD,function(x) any(is.na(x)))])
   if(isTRUE(na.treatment=="delete")) {
     return(na.omit(data))
@@ -144,7 +134,7 @@ PopMiss.data.table <-function(data,na.treatment,replace=NULL){
 }
 
 #' @export
-PopMiss.matrix <- function(data,na.treatment,replace=NULL){
+PopMiss.matrix <- function(data,na.treatment,replace){
 	if(identical(na.treatment,"delete")) warning("na.treatment is \"delete\" and 'data' is a matrix. This only works correctly if whole rows are missing")
 	matrix(PopMiss(as.vector(data),na.treatment,replace),ncol=ncol(data))
 }
\ No newline at end of file
diff --git a/R/resiPlot b/R/resiPlot.r
similarity index 99%
rename from R/resiPlot
rename to R/resiPlot.r
index 9286597..6288764 100644
--- a/R/resiPlot
+++ b/R/resiPlot.r
@@ -20,7 +20,6 @@
 #' @importFrom ggplot2 aes ggplot
 #' @importFrom grid grid.newpage viewport pushViewport
 #' @export resiPlot
-#' @examples
 #' 
 
 resiPlot <- function(act,pred,bucket=20){
diff --git a/README.md b/README.md
index fae02d0..79456a4 100644
--- a/README.md
+++ b/README.md
@@ -43,6 +43,9 @@ iris.mod <- gbm(Species ~ ., distribution="multinomial", data=iris, n.trees=2000
 tree_data <- tree2data(iris.mod,1)
 sankeyNetwork(tree_data[[1]],tree_data[[2]],Source="src",Target="tar",Value="value",NodeID="name")
 
+
+* `resiPlot`: This function assess the residual using given actual and predicted values.
+
 ```
 
 ### Getting Started
diff --git a/man/resiPlot.Rd b/man/resiPlot.Rd
new file mode 100644
index 0000000..f5067a5
--- /dev/null
+++ b/man/resiPlot.Rd
@@ -0,0 +1,32 @@
+% Generated by roxygen2 (4.1.1): do not edit by hand
+% Please edit documentation in R/resiPlot.r
+\name{resiPlot}
+\alias{resiPlot}
+\title{resiPlot}
+\usage{
+resiPlot(act,pred,bucket=20)
+}
+\arguments{
+\item{act}{numerical vector for actual observation.}
+
+\item{pred}{numerical vector for model preidctions.  It must have the same length as act.}
+
+\item{bucket}{Integer. It specifies the number of bucket of the AvsE plot.}
+}
+\description{
+This function assess the residual using given actual and predicted values.
+}
+\details{
+Currently, the residual in this function is defined as: Residual = actual - predicted.  I don't use `resi` or `reisdual` function
+from `stats` package because this function will be used for much wider model assess (e.g. `randomFoest`, `gbm`), but 2 functions
+mentioned about can only applied to `glm` and `lm`.  May code in some other residual function.
+
+This function will give 3 plots:
+Residual vs Prediction: This plot is used to assess the baise and heterogeneity
+Residual histogram: Check the residual distribution.
+AvsE plot: The aggregated (by provided number of bucket) average actual and predicted value, with a diagnal line for comparison.
+}
+\author{
+Sixiang Hu
+}
+