Re: [ferret_users] Problem with 6 hourly to daily average

[Satyesh Ghetiya <satyeshghetiya@xxxxxxxxx>]

Respected Martin and William,

Thank you very much. The hints provided by you are very helpful to me.

Thanks again.

Regards, 

G Satyesh

On Sun, Feb 10, 2019 at 3:52 AM Martin Schmidt <martin.schmidt@xxxxxxxxxxxxxxxxx> wrote:

Hi,

both versions of the syntax give the same result. I didn't know this.

yes? define
axis/t="1-jan-2000:00:00":"2-jan-2000:00:00":1/unit=hours/t0="1-jan-2000:00:00"
tax

yes? list t[gt=tax]

yes? define axis/t="1-jan-2000 00:00":"2-jan-2000
00:00":1/unit=hours/t0="1-jan-2000 00:00" tax
Replacing definition of axis TAX

yes? list t[gt=tax]

Sorry for the confusion,

Martin


On 2/9/19 9:42 PM, William Kessler wrote:
> No, Satyeesh's time syntax is correct: there must be a ':' between the day and the hour in a time specification. That's why the quotes are needed; otherwise the hour would be interpreted as another argument (e.g., delta-t). I would have thought the minutes also needed to be specified but apparently not.
>
> But if you want a daily average, it would be safer to define it explicitly, depending on what exactly you mean by a daily average.
> If you intend it to be the mean of the values at hours 0,6,12,18, then
>
> ! make an explicit running 4-timestep average:
> let var_daily_ave = (var+var[l=@shf:1]+var[l=@shf:2]+var[l=@shf:3])/4
>
> Now subsample at hour 0:
>
> define axis/t="01-jan-1993":"31-dec-2017":1/units=day t24h
> let var_d = var_daily_ave[gt=t24h]
>
> ! check your work for an interval short enough to see what's happening:
> plot/t=some_start_date:some_end_date var,var_d
>
>
>
>> On Feb 9, 2019, at 6:50 AM, Martin Schmidt <martin.schmidt@xxxxxxxxxxxxxxxxx> wrote:
>>
>> Hi,
>>
>> seems the syntax of your times is not correct. I should be:
>> define axis/t="01-jan-1993 00:00":"31-dec-2017 18:00"/units=days/npoints=36524 t6
>>
>> The same for the other axis.
>> Best,
>> Martin
>> Am 09.02.2019 um 15:35 schrieb Satyesh Ghetiya:
>>> Dear all,
>>> I am wanting to convert 6 hourly (0,6,12,18 hr) data to daily average.
>>>
>>> 6 hourly existing time axis, of variable var, is:
>>> define axis/t="01-jan-1993:00:00":"31-dec-2017:18:00"/units=days/npoints=36524 t6
>>>
>>> and daily time axis (on which I want my final average) is:
>>> define axis/t="01-jan-1993:09":"31-dec-2017:09":24/units=hours t9
>>>
>>> Now, following step should give my desired daily final mean:
>>> let var_d=var[gt=t9@ave]
>>>
>>> (Above method is given by the thread :https://www.pmel.noaa.gov/maillists/tmap/ferret_users/fu_2004/msg00540.html )
>>>
>>> But the problem is:  var_d is not being calculated except at l=1. I have improvised all steps and all seem very fine, so var_d should give all daily values. But, except at l=1, all other l's are showing 'No Valid Data'. Any experience in this regard ?
>>>
>>> Hope to hear soon.
>>>
>>> Regards,
>>> G Satyesh
>>>
>