diff --git a/NAMESPACE b/NAMESPACE
index d75f824..c1a7cea 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -1 +1,2 @@
 exportPattern("^[[:alpha:]]+")
+importFrom("stats", "quantile")
diff --git a/R/meanimpute.R b/R/meanimpute.R
index cc7cf5e..f7f79e5 100644
--- a/R/meanimpute.R
+++ b/R/meanimpute.R
@@ -1,4 +1,5 @@
 #' Meanimputation
+#' @param x A vector
 #' @export
 meanimpute <- function(x) {
   x[is.na(x)] <- mean(x, na.rm = TRUE)
diff --git a/R/transform_log.R b/R/transform_log.R
new file mode 100644
index 0000000..004f883
--- /dev/null
+++ b/R/transform_log.R
@@ -0,0 +1,19 @@
+#' transform_log 
+#' Transform numerical values into their log values
+#' @param x A vector
+#' @return logarithm of x
+#' @export 
+#' @examples
+#' transform_log(1)
+#' transform_log(c(1, 2, 3, 4, 5))
+#' 
+transform_log <- function(x) { 
+  if (!is.numeric(x)) {
+    warning("transform_log: Expecting numeric argument")
+  }
+  x_badval <- is.na(suppressWarnings(as.numeric(x)))
+  x[x_badval] <- 1
+  y <- log(as.numeric(x))
+  y[x_badval] <- NA
+  y
+} 
\ No newline at end of file
diff --git a/R/windsorize.R b/R/windsorize.R
index b4e15e6..de18782 100644
--- a/R/windsorize.R
+++ b/R/windsorize.R
@@ -1,10 +1,30 @@
 #' Windsorize
 #'
-#' Do some windsorization.
+#' set all outliers to a specified percentile of the data; 
+#' a 90% winsorization would see all data below the 5th percentile set 
+#' to the 5th percentile, 
+#' and data above the 95th percentile set to the 95th percentile.
+#' 
+#' @param x A vector.
+#' @param p A quantile.
+#' @return dataset with trimmed outliers with 10% percentile
+#' @examples
+#' windsorize(c(3,4,4,3,4,5,1))
 #' @export
 windsorize <- function(x, p = .90) {
-  q <- quantile(x, p)
-  x[x >= q] <- q
+  if (length(x) == 0) stop("argument should not be a empty vector")
+  if (all(is.na(x))) {
+    stop("argument should not be a vector containing only NA")
+  }
+  if (!is.numeric(x)) stop("argument should be a numeric vector")
+  if (!is.numeric(p)) stop("argument should be a number from 0 to 1")
+  if (p < 0 || p > 1) {
+    stop("p invalid percentale. Expected values from 0 to 1")
+  }
+  q_lower <- quantile(x, (1-p)/2)
+  q_upper <- quantile(x, 1 - (1-p)/2)
+  x[x <= q_lower] <- q_lower
+  x[x >= q_upper] <- q_upper
   x
 }
 
diff --git a/man/meanimpute.Rd b/man/meanimpute.Rd
index 8139e8f..77f2fbc 100644
--- a/man/meanimpute.Rd
+++ b/man/meanimpute.Rd
@@ -6,6 +6,9 @@
 \usage{
 meanimpute(x)
 }
+\arguments{
+\item{x}{A vector}
+}
 \description{
 Meanimputation
 }
diff --git a/man/transform_log.Rd b/man/transform_log.Rd
new file mode 100644
index 0000000..c5b287c
--- /dev/null
+++ b/man/transform_log.Rd
@@ -0,0 +1,24 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/transform_log.R
+\name{transform_log}
+\alias{transform_log}
+\title{transform_log 
+Transform numerical values into their log values}
+\usage{
+transform_log(x)
+}
+\arguments{
+\item{x}{A vector}
+}
+\value{
+logarithm of x
+}
+\description{
+transform_log 
+Transform numerical values into their log values
+}
+\examples{
+transform_log(1)
+transform_log(c(1, 2, 3, 4, 5))
+
+}
diff --git a/man/windsorize.Rd b/man/windsorize.Rd
index 832c3cb..2a0ff5d 100644
--- a/man/windsorize.Rd
+++ b/man/windsorize.Rd
@@ -6,6 +6,20 @@
 \usage{
 windsorize(x, p = 0.9)
 }
+\arguments{
+\item{x}{A vector.}
+
+\item{p}{A quantile.}
+}
+\value{
+dataset with trimmed outliers with 10% percentile
+}
 \description{
-Do some windsorization.
+set all outliers to a specified percentile of the data; 
+a 90% winsorization would see all data below the 5th percentile set 
+to the 5th percentile, 
+and data above the 95th percentile set to the 95th percentile.
+}
+\examples{
+windsorize(c(3,4,4,3,4,5,1))
 }
diff --git a/tests/testthat.R b/tests/testthat.R
new file mode 100644
index 0000000..8adbfff
--- /dev/null
+++ b/tests/testthat.R
@@ -0,0 +1,4 @@
+library(testthat)
+library(datacleaner)
+
+test_check("datacleaner")
diff --git a/tests/testthat/test_tranform_log.R b/tests/testthat/test_tranform_log.R
new file mode 100644
index 0000000..70bae1c
--- /dev/null
+++ b/tests/testthat/test_tranform_log.R
@@ -0,0 +1,11 @@
+context("tranform_log")
+library(datacleaner)
+test_that("tranform_log is correct", {
+  expect_equal(as.character(transform_log(c(2, 2, 2, 2, 3))), as.character(c(0.693147180559945, 0.693147180559945, 0.693147180559945, 0.693147180559945, 1.09861228866811)))
+  expect_equal(as.character(transform_log(c(2, 3, NA))), as.character(c(0.693147180559945, 1.09861228866811, NA)))
+})
+
+test_that("unexpected parameters", {
+  expect_warning(t <- transform_log(c(2, 3, "NA")), "transform_log: Expecting numeric argument")
+  expect_equal(as.character(t), as.character(c(0.693147180559945, 1.09861228866811, NA)))
+})
\ No newline at end of file
diff --git a/tests/testthat/test_windorize.R b/tests/testthat/test_windorize.R
new file mode 100644
index 0000000..5e0beb4
--- /dev/null
+++ b/tests/testthat/test_windorize.R
@@ -0,0 +1,17 @@
+context("Windsorize")
+library(datacleaner)
+test_that("windorizing is correct", {
+  expect_equal(windsorize(c(2,2,2,2,3),.9), c(2,2,2,2,2.8) )
+  expect_equal(windsorize(c(2,2,2,2,1),.9), c(2,2,2,2,1.2) )
+})
+
+test_that("unexpected parameters", {
+  expect_error(windsorize(c(NA,NA,NA), .9), "argument should not be a vector containing only NA")
+  expect_error(windsorize(c(), .9), "argument should not be a empty vector")
+  expect_error(windsorize(c(1,2,3,"4"), .9), "argument should be a numeric vector")
+  expect_error(windsorize(c(1,2,3,4), ".9"), "argument should be a number from 0 to 1")
+  expect_error(windsorize(c(1,2,3,4), -1), "p invalid percentale. Expected values from 0 to 1")
+  expect_error(windsorize(c(1,2,3,4), 1.2), "p invalid percentale. Expected values from 0 to 1")
+  expect_error(windsorize(c(1,2,3,NA), .9))
+  
+})