I am just starting to learn about KnitR and the use of Markdown in generating R documents and reports. This looks to be perfect for a lot of the day to day reporting that I
Now knitr (since version 1.3) package include the kable function for a creation tables:
> library(knitr)
> kable(head(iris[,1:3]), format = "markdown")
| Sepal.Length| Sepal.Width| Petal.Length|
|-------------:|------------:|-------------:|
| 5,1| 3,5| 1,4|
| 4,9| 3,0| 1,4|
| 4,7| 3,2| 1,3|
| 4,6| 3,1| 1,5|
| 5,0| 3,6| 1,4|
| 5,4| 3,9| 1,7|
UPDATED: if you get raw markdown in a document try setup results = "asis" chunk option.