set xrange[0:10]
set yrange[0:10]
set zrange[0:10]
set zeroaxis lt -1 lw 1

unset tics

set style arrow 1 size character 2,20 filled linewidth 1
set arrow 1 from 0,0,-5 to 0,0,10 arrowstyle 1      # z軸
set arrow 2 from 0,0,-5 to 0,10,-5 arrowstyle 1     # y軸
set arrow 3 from 0,0,-5 to 10,0,-5 arrowstyle 1     # x軸

set label "z" at 0.7,0,  9.5 font "Arial,12"
set label "y" at 0.7,9,  -5  font "Arial,12"
set label "x" at 9,  0.5,-4  font "Arial,12"


set style arrow 1 size character 2,20 filled linewidth 4
set arrow 4 from 0,0,-5 to 0,0,7 arrowstyle 1      # B_0
set arrow 5 from 0,0,-5 to 0,7.5,-5 arrowstyle 1     # v
set arrow 6 from 0,0,-5 to 7,0,-1.5 arrowstyle 1     # k

set label "B_0" at 0.5,0,6  font "Arial,12"
set label "v_1"   at 0.7,6,-5 font "Arial,12"
set label "k"   at 6,0,-3 font "Arial,12"


splot "coordinate.txt" notitle
#splot "coordinate2.dat" with lines


set terminal png
set output "CO1.png"
replot