Visualization of the temporal development of a single node value at fixed position x0 for example
for the temperature value T (x0, t) or a displacement.
Starting point is a two column datafile like gnuplots/example_v1/V1.dat holding the
values for t and T(t), in the example we use t=0:0.1:10 and T(t)=exp(t/10)+cos(t) and move the T-values 12.3 with the 'using'
command inside the gnuplot script.
After creating the gnuplot script gnuplots/example_v1.txt and registration of this
script in the Makefile by adding the line
Plotting colored scalar fields, like in the example example_v3.pdf the norm |u| of the displacement,
or temperature values needs a datafile which holds in a line 4 (x1,x2,v) triplets for the node values of an element.
As an example see example_v3/frame1.txt.