Plotting arrows with gnuplot

Question

I have data generated in a simulation. The generated data file looks something like this:

1990/01/01 99
1990/01/02 92.7
1990/01/03 100.3
1990/01/04 44.2
1990         


        

Answer 1

Although the question is quite old, here is my answer.

One can use the vectors plotting style, which can use variable arrowstyles based on a column's value:

set style arrow 1 backhead
set style arrow 2 head
set yrange[0:*]
set xdata time
set timefmt "%Y/%m/%d"
plot "simulation.dat" using 1:2 with line,\
     "" using 1:2:(0):(-$2):($3 == 0 ? 1/0 : $3) with vectors arrowstyle variable

It the value of a column is 1/0, the point is considered as undefined and is skipped.