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Re: [ferret_users] Plotting Argo data



Hi Karthik,
If you are plotting a variable in time, then Ferret automatically chooses labels on the time axis according to the range of time you have specified.  The line that is drawn on a line plot just connects the points.  If you are plotting a variable in 2 dimensions, then indeed Ferret fills in data between coordinate points using an algorithm to make contour lines or color contoured areas; or you can use the SHADE command to do a raster plot. It fills each grid box with color.

I'll do a quick example and the point you to the parts of the documentation that you should look at for further details.

For example, let's define a time axis with 10 day intervals and plot a variable on it.  This axis is regularly spaced; if yours is irregularly spaced it will still be drawing lines between the individual points.  We'll use PLOT/LINE/SYMBOL to mark the location of the variable at each coordinate location.
yes? define axis/t="1-oct-2000":"1-oct-2001":10/units=days/t0=1-jan-2000  timeaxis10
yes? let tt = t[gt=timeaxis10]
yes? let var = cos(tt/20)
yes? plot var

yes? plot/line/symbol var     ! mark the points with a symbol

yes? plot/line/symbol/t=1-oct-2000:1-nov-2000 var  ! a shorter subset
If you want to plot a short section between two dates which don't correspond to the coordinate points, then this would happen:
yes? plot/line/symbol/t=20-oct-2000:24-oct-2000 var
 **ERROR: illegal limits: One-point independent axis: Requires a /HLIMIT or /VLIMIT specification
Here you would need to define a new time axis at a finer resolution and regrid the data to that new axis.  Continuing the example, here is a daily time axis, and our variable regridded to it.
yes? define axis/t="1-oct-2000":"1-oct-2001":1/units=days/t0=1-jan-2000  timeaxis1
yes? let var_day = var[gt=timeaxis1]
yes? plot/line/symbol/t=1-oct-2000:1-nov-2000 var_day 
In the Ferret Users Guide, I would suggest looking through the first several chapters.  The regridding section is in Chapter 4, and that chapter would be especially useful to you. It talks about grids and regions will help you to understand how data is organized and how to interact with it.

Ansley

Balaguru, Karthik wrote:
  Dear Ferret Users,

       I have a question regarding plotting of Argo data using ferret. Once I've transformed the data as shown in a tutorial, I have been able to perform all the normal functions. But I have a small problem. The time step typically for Argo is around 10 days. Let's say l = 10 is Oct 20 and l = 11 is Nov 4. When I plot the data from l=10:11, it also shows days in between these two dates. I wonder how it is able to get the information in between these dates. Also if I want to plot until a day in between l= 10 and l=11, say until Oct 27th how do I do it. Any help would be greatly appreciated. Thanks!

  Karthik.
  

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