I am trying to make a graph of some floor/ceiling functions for examplep the floor of 3x+2 like this: [http://www.wolframalpha.com/input/?i=graph+of+floor%283x%2B2%29#*=*.](http://www.wolframalpha.com/input/?i=graph%20of%20floor%283x%2b2%29#_=_)

However, I searched through the PFGPlots manual and did not find a mention of that. Does anyone know how to do this in LaTeX or PGFplots?