Re: Overlay/plot and vector direction info

[Ansley Manke <ansley@xxxxxxxxxxxxx>]

Hello Flore,
(no need to address a question to Ferret Users and Ansley,
the Ferret developers are all on the users' list, and will answer
as we have time to do so - particularly questions that might 
not
be addressed by the user community.)

To overlay two variables on the same plot, or plot them with the
VECTOR command, you need to have them on the same grid.
If I understand your question, one is on a grid that is a subset of the
other.   You can set the region to match the range of the smaller
one, and then regrid either variable to the grid of the other.  Then
you can plot them using the VECTOR command.  Note that if they
are in two different data sets you will need to specify the data set along
with the variable name.  For example, if taux is on a particular range of
coordinates and I regrid tauy to the grid of taux :
 
    LET tx = taux[d=1]
    LET ty = tauy[d=2]
    SET REGION/x=200:300/y=20S:40N
    VECTOR  tx, ty[d=2,gx=tx,gy=tx]

Once you compute your  value  in degrees you can put it on the plot
using the label command.  The grave quotes force the variable to be
evaluated at a location so the number itself goes on the plot.

    LET direc =  cos(tauy/taux)* 180/3.14159    ! or whatever is the correct
                                                                         ! calculation for wind stress direction
    LABEL/USER 230, -5, 0, 0, 0.15, "`direc[x=230,y=5s]`"

! Or, use the PRECISION keyword to control the formatting of the number.
    LABEL/USER 230, -5, 0, 0, 0.15, "`direc[x=230,y=5s],PREC=2`"
 

Ansley

Flore Mounier wrote:

dear  Ansley and ferret users
The  two following questions concern Taux and Tauy data that are zonal and meridional wind stress components in N/m2.

Question 1:
I have got two sets of data, in terms of coordinates they have the same but in term of grid space they don't have the same size.
I need to plot some data from each of the set of data together but it doesn't work properly.  Do I have to regrid one of the set or is their a other and easier way to put the two plots on the same graphic?
Question 2:
The two components are associated and constitute a vector that has a specific direction. I would like to plot this direction in deg (0 to 360) on some specific point of the area I am studying. How can I get some information about the direction of the vectors and plot this information?

Any suggestion will be really welcome,
Thank you in advance,
Flore
 

-- 
Flore MOUNIER
Ecole Nationale Superieure des Techniques Avancees (ENSTA)
Unite d'Enseignement et de Recherche en Mecanique (UME)
Chemin de la Huniere  91761 Palaiseau cedex
FRANCE
tel : 01 69 31 97 56
fax : 01 69 31 99 97
e-mail: mounier@enstay.ensta.fr

 

--
Ansley Manke  Pacific Marine Environmental Laboratory  Seattle WA  (206)526-6246