r - RGDAL won't install -

i can't rgdal install in r. i'm using ubuntu 12.04.

configure: error: gdal-config not found or not executable. error: configuration failed package ‘rgdal’ * removing ‘/home/james/r/x86_64-pc-linux-gnu-library/3.2/rgdal’ warning in install.packages :   installation of package ‘rgdal’ had non-zero exit status 

i found solutions said this:

sudo apt-get install aptitude sudo aptitude install libgdal-dev  sudo aptitude install libproj-dev 

i follow these through, accepting 'yes' when prompted, afterwards same original error. doesn't resolve it. wonder whether should downgrading perhaps?

thanks, james.