diff --git a/DESCRIPTION b/DESCRIPTION
index d1ca2b1..c2eed51 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,6 +1,6 @@
 Package: CTUHelpR
 Title: Small helper functions used in the CTU Basel
-Version: 0.0.3
+Version: 0.0.4
 Author:
     c(person(given = "CTUBasel",
              role = c("cph")),
@@ -29,7 +29,8 @@ RoxygenNote: 7.1.0
 Depends:
     R (>= 3.5)
 Imports:
-    readr
+    readr,
+    assertthat
 Suggests:
     knitr,
     lintr,
diff --git a/NAMESPACE b/NAMESPACE
index 8212ed8..413316d 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -1,6 +1,8 @@
 # Generated by roxygen2: do not edit by hand
 
+export(na_to_level)
 export(Median)
 export(Sum)
 export(print_file_content)
+importFrom(assertthat,assert_that)
 importFrom(readr,read_file)
diff --git a/NEWS.md b/NEWS.md
index eb00ae0..77f7a0b 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,3 +1,7 @@
+
+# CTUHelpR 0.0.4
+* the `na_to_level()` function has been added to the package
+
 # CTUHelpR 0.0.3
 * the `Median()` function has been added to the package
 
diff --git a/R/na_to_level.R b/R/na_to_level.R
new file mode 100644
index 0000000..f596ab4
--- /dev/null
+++ b/R/na_to_level.R
@@ -0,0 +1,19 @@
+#' This functions replaces all NA's in a factor to a level with specified name.
+#'
+#' @param x a factor
+#' @param name character - the name of the new level (default: N/A)
+#' @return The same factor with renamed NA
+#' @importFrom assertthat assert_that
+#' @export
+#' @examples
+#' na_to_level(factor(c("a","b", "b", NA))) # Levels: a b N/A
+na_to_level <- function(x, name = "N/A") {
+  assert_that(is.factor(x))
+  
+  if(!(name %in% levels(x))) {
+    x <- factor(x, levels = c(levels(x), name))
+  }
+  x[is.na(x)] <- name
+  
+  return(x)
+}
diff --git a/README.md b/README.md
index fb38cf0..0e89b4e 100644
--- a/README.md
+++ b/README.md
@@ -1,8 +1,7 @@
 
 <!-- README.md is generated from README.Rmd. Please edit that file -->
 
-
-# CTUHelpR ![travis](https://api.travis-ci.com/CTU-Basel/CTUHelpR.svg?branch=master) [![codecov](https://codecov.io/github/CTU-Basel/CTUHelpR/branch/master/graphs/badge.svg)](https://codecov.io/github/CTU-Basel/CTUHelpR) [![](https://img.shields.io/badge/dev%20version-0.0.3-blue.svg)](https://github.com/CTU-Basel/CTUHelpR) [![AppVeyor Build Status](https://ci.appveyor.com/api/projects/status/github/CTU-Basel/CTUHelpR?branch=master&svg=true)](https://ci.appveyor.com/project/CTU-Basel/CTUHelpR)
+# CTUHelpR ![travis](https://api.travis-ci.com/CTU-Basel/CTUHelpR.svg?branch=master) [![codecov](https://codecov.io/github/CTU-Basel/CTUHelpR/branch/master/graphs/badge.svg)](https://codecov.io/github/CTU-Basel/CTUHelpR) [![](https://img.shields.io/badge/dev%20version-0.0.4-blue.svg)](https://github.com/CTU-Basel/CTUHelpR) [![AppVeyor Build Status](https://ci.appveyor.com/api/projects/status/github/CTU-Basel/CTUHelpR?branch=master&svg=true)](https://ci.appveyor.com/project/CTU-Basel/CTUHelpR)
 
 ## Installing from github with devtools
 
diff --git a/man/na_to_level.Rd b/man/na_to_level.Rd
new file mode 100644
index 0000000..5f15078
--- /dev/null
+++ b/man/na_to_level.Rd
@@ -0,0 +1,22 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/na_to_level.R
+\name{na_to_level}
+\alias{na_to_level}
+\title{This functions replaces all NA's in a factor to a level with specified name.}
+\usage{
+na_to_level(x, name = "N/A")
+}
+\arguments{
+\item{x}{a factor}
+
+\item{name}{character - the name of the new level (default: N/A)}
+}
+\value{
+The same factor with renamed NA
+}
+\description{
+This functions replaces all NA's in a factor to a level with specified name.
+}
+\examples{
+na_to_level(factor(c("a","b", "b", NA))) # Levels: a b N/A
+}
diff --git a/tests/testthat/test-na_to_level.R b/tests/testthat/test-na_to_level.R
new file mode 100644
index 0000000..5346943
--- /dev/null
+++ b/tests/testthat/test-na_to_level.R
@@ -0,0 +1,12 @@
+context("na to level")
+
+test_that("Test fail", {
+  expect_error(na_to_level(123))
+  expect_error(na_to_level("abc"))
+})
+
+test_that("Test output", {
+  expect_equal(as.vector(na_to_level(factor(c("a","b", "b", NA)))), 
+               as.vector(factor(c("a","b", "b", "N/A"))))
+  expect_true(is.factor(na_to_level(factor(c("a","b", "b", NA)))))
+})