Some of Takin's program modules optionally require Gnuplot. It is especially recommended in order to have a live-display of the progress in the convolution fitter. The steps to correctly install Gnuplot and its graphical output terminals are given as follows (pick the package manager which applies for your system):
apt-get install gnuplot gnuplot-qt
dnf install gnuplot
yum install gnuplot
pacman -S gnuplot
brew install gnuplot --with-qt --with-x11