Rahat,

R code chunks in an Rmd file need to start with ```{r}  Also usually best to give the code chunks name and specify whether or not you want the the code to be evalauted by R or not.

For the purposes of this Blog Post it is likely you do not want them evaluated.  

Jeff

p.s. I'll go ahead and accept the merge request and make the changes myself.  I'll also make some other comments here!