Simple plotting with gnuplot

from 1 column data of sequential var's:

gnuplot> plot 'data.dat' axes x1y2 with lines 

from 2d (x and y)

gnuplot> plot 'data.dat' with lines 

to output in external file:
ex1:

set terminal svg size 800 600
set out "test.svg"
plot sin(x)

ex2:

set terminal png size 800 600
set out "test.png"
plot 'c.dat' with lines