I came across this fantastic function called 

> 
> within {base}
> 
> 
> 

I use it more often now than the much hyped 

> 
> mutate {dplyr}
> 
> 
> 

My question is, why is **within()** having such a peculiar format with assignment operators used **<-** instead of the usual **=** for args; How is it different from **mutate** other than what is given in this fantastic article I found. I am interested to know the underlying mechanism.
[Article of Bob Munchen - 2013](http://r4stats.com/2013/01/22/comparing-tranformation-styles/)