title: R in tcl/tk missing
body: <p>While installing a package in R, I am getting error message in mu ubuntu 16.04 machine as shown belo dur t lack of tcl/tlk header. How to resolve it?</p>
  
  <pre>
  gcc -std=gnu99 -I/usr/share/R/include -DNDEBUG -I/usr/include/tcl8.6 -I/usr/include/tcl8.6     -fpic  -g -O2 -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 -g  -c tcltkimg.c -o tcltkimg.o
  tcltkimg.c:2:16: fatal error: tk.h: No such file or directory
  </pre>