I'm having the same issue as this question:
When I open any .Rnw file, R Studio says that I have no TeX Distribution installed: I'm using Ubuntu 14.04 w/ Gnome and TeXLive 2014.
I include the line PATH=/usr/local/texlive/2014/bin:${PATH}
in the Renviron.site file, which now looks like:
## Emacs please make this -*- R -*-
## empty Renviron.site for R on Debian
##
## Copyright (C) 2008 Dirk Eddelbuettel and GPL'ed
##
## see help(Startup) for documentation on ~/.Renviron and Renviron.site
# ## Example ~/.Renviron on Unix
# R_LIBS=~/R/library
# PAGER=/usr/local/bin/less
# ## Example .Renviron on Windows
# R_LIBS=C:/R/library
# MY_TCLTK="c:/Program Files/Tcl/bin"
# ## Example of setting R_DEFAULT_PACKAGES (from R CMD check)
# R_DEFAULT_PACKAGES='utils,grDevices,graphics,stats'
# # this loads the packages in the order given, so they appear on
# # the search path in reverse order.
PATH=/usr/local/texlive/2014/bin:${PATH}
However the problem persists. How can I fix this and run Sweave or knitR?