[Re: Time axis from variables]

[Tony Jolibois <tjolibois@xxxxxx>]

                Hi Ansley,

Excuse me I didn't send details. Here it is :
The data contains year, month, day, hour-minute-second, location and other things :
buoy.dat :
[5] 2002-07-28 13:59:50 09435 28700 NM  T  2   48.989  339.229
[5] 2002-07-28 14:37:53 09435 28700 NH  T  2   48.987  339.230
[5] 2002-07-28 15:13:44 09435 28700 NL  T  3   48.989  339.245
[5] 2002-07-28 16:05:40 09435 28700 ND  T  1   48.988  339.252
[5] 2002-07-28 16:56:52 09435 28700 NL  T  1   48.989  339.269
[5] 2002-07-28 17:40:02 09435 28700 NJ  T  3   48.996  339.281
[5] 2002-07-28 19:18:48 09435 28700 NJ  T  2   48.995  339.318
[5] 2002-07-28 19:29:02 09435 28700 NK  T  1   48.999  339.343
       --------- time ----------                                            lat            lon

Here is the script I tried to create the time axis :

FILE/FORMAT=delim/delimiter="\b,\t"/type="text,date,time,numeric,numeric,text,text,numeric,latitude,longitude"/EZ bouee_28700-32790.txt
LET days_2001 = DAYS1900(2002,1,1)
LET day_frac = v3/24
LET tstep = v2 - days_2001 + day_frac
list tstep
 1      /    1:  175.7
 2      /    2:  175.7
 3      /    3:  175.7
 4      /    4:  175.7
 5      /    5:  175.8
 6      /    6:  175.8
 7      /    7:  175.9
 8      /    8:  175.9
...
So you can see that when I try to create the time axis, ferret says 

DEFINE axis/T/T0=1-jan-2001/UNIT=days ttaxis=tstep[L=1:50]
 **ERROR: improper grid or axis definition: data for DEFINE AXIS/FROM_VARIABLE is not monotonic

Thanks for your response,
Tony

2002-07-28 13:59:50

Ansley Manke wrote:

Hi Tony,
What are your timestps like?  Units of seconds over the course
of a month?  Or what?  Are they regularly spaced or irregular?

Ansley Manke

Tony Jolibois wrote:

         Hi ferreters,

I'm trying to plot Argos buoy location with a time axis.
The data are in ascii file, so I read this page to create my time axis : http://ferret.pmel.noaa.gov/Ferret/FAQ/axes_and_data/time_axis_from_variables.html.
In the end of the page, you can find that :

Note that Ferret variables are represented as single precision real numbers.  (Axes are represented in double precision, but we are using a variable to define
the axis and that variable is single precision.) If your timestep is small, such as minutes, and your times are a century or more after 1-jan-1900, you will need
to use a time origin later than 1-Jan-1900

The problem is that my timestep is so small that enven if I use a new time origin some step which was not equal are equal after the calculation.
Can someone know how can I define a variable with a better precision, or tell me what can I do to define a good time axis ?

Thanks in advance,
Tony