Blender and Gnuplot are rather different kind of program.
From Blender's site you can read
It supports the entirety of the 3D pipeline—modeling, rigging, animation, simulation, rendering, compositing and motion tracking, even video editing and game creation. Advanced users employ Blender’s API for Python scripting to customize the application and write specialized tools; often these are included in Blender’s future releases.
Gnuplot instead
is a portable command-line driven graphing utility
really cosy; you can create scientific plots, perfect for Latex/pdf/eps and scientific publications or thesis.
It is not able to do any 3d rendering as instead povray
The Persistence of Vision Raytracer is a high-quality, Free Software tool for creating stunning three-dimensional graphics.
Povray and gnuplot can quick take advantage of bash/awk programming.