Judging by the number of people asking on the forums, this a very common FAQ.
Ensure that the Gnuplot binary
folder is registered in the PATH environment variable so that you can call the
Gnuplot executable from any folder.
You may find that Gnuplot
reports that the wxt is an unknown terminal type; in which case, use the
following command :
Uninstall your current version
of Gnuplot and then install the +wxt variant.
port
variants gnuplot to list available variants.
sudo
port install gnuplot +wxwidgets
Note, after this I had to reboot
MacOS to enable Gnuplot to recognize the new terminal types.
Under Linux you need to install
both Gnuplot and Gnuplot-X11 :
sudo
apt-get install gnuplot
sudo
apt-get install gnuplot-x11