I have zero experience using gnuplot and all I am trying to figure out is the meaning of the line I found on web, so that I can code it up using python.
gnuplot > p "kaccum.dat" i 30 u 1:2 w l, "kaccum.dat" i 30 u 1:8 w l
It means that once the execution of the commands is finished, the created figure remains on the screen (p=persistent), that plots the data of kaccum.dat file corresponding to index 30 (i=within the same column, it is assumed that the data is ordered as in groups, perhaps each group separated by a line or black space, and refers to "group 30"), using the values of column 1 on the X axis and column 2 on the Y axis (u 1:2), and join the points with a line (w l = with line).