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Re: [ferret_users] Trying to understand logic behind stick plot

Have you been able to read your data into Ferret? UTC simply means Coordinated Universal Time, but what is the data unit?  Seconds, maybe?  and since what time origin? Your data source should tell you more than just "UTC".

Ferret will be able to convert those data to time steps once one knows that.  You would read in the three variables, define a time axis using the first one, and RESHAPE your u and v components to that time axis. Fill in the right things in the DEFINE AXIS command, and you should be set.
yes? file/var="tsec, zero, u, v" my_data.dat
yes? define axis/t/units=seconds/t0="???" timeax = tsec
yes? let ucomp = reshape(u,t[gt=timeax])
yes? let vcomp = reshape(v,t[gt=timeax])
It would be a good idea  to add /UNITS=  on the  LET commands to give the velocity components their correct units.  Then you should be able to try the stick_vectors script to make a plot.


On 6/30/2014 5:42 AM, 'Don DNA' via _OAR PMEL Ferret Users wrote:
I read answer from ferret userlist regarding stick plot from here, and I don't have much knowledge about ferret, even to read source code

I have "UTC date, u - component, v-component " I am interested to calculate time shift, can someone please help me to calculate time shift for line segments,

My data looks something like this

UTC data, Zero, U-comp, V-component
 379987200000,0, -3.969,0.596
 382665600000,0, -4.578,-1.001
 387763200000,0, -1.622,1.58

Can someone please explain me, time shift for above input, I actually did not understand this "from (c*t, 0) to (c*t+u(t), v(t))", if I just add utc date to U(t) - component I will get very close value and I will not get slope, please help me..

Thanks in advace.

- Dona

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