[Gnuplot-info] Vector plot with time x-axis

[David B. <bro...@fa...>]

Hi,
I am trying to make a plot of wind vs time. I want time on the X axis, 
the Y axis to be the speed and a fixed size vector at each data point 
indicating the wind direction.

The ideal thing would be if I could specify the deltax and deltay size 
of each vector in pixels, or some other screen coordinate independent of 
the x and y ranges. Is this possible?

I haven't been able to find any information about the above so I assume 
I will need to specify deltax as a time and figure out the right 
scaling. However I haven't been able to get this to work, the vectors 
always have zero length in the X dimension. I have:

...
set xdata time
set timefmt "%m/%d-%H:%M"
...
plot 'foo.txt' using 1:2:3:4 with vectors

Where the data file is like this:
05/17-11:00 6.33660511836 -00/00-00:55 -0.35963594262
05/17-14:00 4.52832308033 00/00-00:40 -0.731311736396
05/17-17:00 3.95676205159 00/00-00:59 0.0217798990928

I have tried various formats for the 3rd column but I have been unable 
to figure out how to make the vector plot work with time on the X axis.

I would greatly appreciate any suggestions,
Thanks,
   Dave