From e25d36c760f78c54d8b31c438b475da848166b5c Mon Sep 17 00:00:00 2001
From: Filip Smolik <phillip.smolik@gmail.com>
Date: Sun, 5 May 2019 11:36:13 +0200
Subject: [PATCH] #22 - function for log-transformation is added.

---
 R/transform_log.R | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)
 create mode 100644 R/transform_log.R

diff --git a/R/transform_log.R b/R/transform_log.R
new file mode 100644
index 0000000..ba11c66
--- /dev/null
+++ b/R/transform_log.R
@@ -0,0 +1,20 @@
+#' transform_log
+#'
+#' log-transformation of a numeric vector. For details about log-transformation please see you basic school math textbook.
+#' @param x a numeric vector
+#' @return log-transformed vector \code{x}
+#' @examples
+#' example_vector=c(1,2,3,4,5,6,7,8,9,10)
+#' transform_log(example_vector)
+#' @export
+
+transform_log <- function(x){
+  
+  if( is.null(x) )    stop("Input vector is not allowed to be NULL.")
+  if( any(is.na(x)) ) stop("There is at least one NA value in input vector.")
+  if( any(x <= 0)  )  stop("There is at least one negative value.")
+  if( any(is.numeric(x) == FALSE) )  stop("There is at least one non-numeric value.")
+  y<-log(x)
+  return(y)
+  
+}
\ No newline at end of file