set output './drag_2015_expt_log.ps' 
set term postscript color enhanced 'Helvetica,18'  
set grid 
set key bot right 
set xlabel 'ln (terminal velocity (m/s))' 
set ylabel 'ln (force of air resistance (N))' 
set title 'Falling coffee filters (Sep 23, 2015) '
plot  './drag_2015.x.log.dat' using 4:3     lt 1 pt 3 lw 3 t ''  ,  -2.11245+1.9008*x with lines lt -1 t 'slope 1.90'  ,  -2.172+(1.9008+0.226)*x with lines lt 2 lc -1 t 'slope 2.13'  ,  -2.042+(1.9008-0.226)*x with lines lt 2 lc -1 t 'slope 1.67'  
set output 
quit 
