gnuplot

LogScale:
set log x 2

change line width
plot "*.dat" w lp lw(linewidth) 10 ps(pointsize)

external links:
http://sparky.rice.edu/~hartigan/gnuplot.html

demo scripts:
http://gnuplot.sourceforge.net/demo/

http://t16web.lanl.gov/Kawano/gnuplot/index-e.html

/* ================================= */
%%% modify value while ploting

plot "accum_1histo_lg_12.0_pp_20.0.dat_bak" u ($1*0.0001):2 w l