Re: [idvusers] What is the best way to iterate over a 3d grid using Jython?

• To: Paul Graham <meteorpaul@xxxxxxxxx>
• Subject: Re: [idvusers] What is the best way to iterate over a 3d grid using Jython?
• From: Tom Whittaker <whittaker@xxxxxxxx>
• Date: Tue, 10 Dec 2013 08:50:43 -0600
```Hi Paul --

I'm not clear on the logic of "(if temp == NaN) then compute

Can you send me (off-line?) your web bulb computation formula?  I'd
like to see what additional logic is in there that prevents you from
using VisAD "built-in" arithmetic.  (I'm always looking for ideas for
new functions to put into JPythonMethods).

tom

On Mon, Dec 9, 2013 at 3:59 PM, Paul Graham <meteorpaul@xxxxxxxxx> wrote:
> Hi Tom,
>
> Thanks for your help.  I figured out a method after some experimentation and
> realised I could not use the visad logic.  My algorithm works point-wise,
> which requires having to step through each point individually.  Essentially,
> I modified existing code for substitution, found in IDV's Jython library:
>
> def wetbulb(temp,dewpt):
>    from java.lang import Math
>    tempData = temp.clone();
>    dewptData = dewpt.clone();
>    presData = extractPressureFromNWPGrid(tempData);
>    wetbulbData = temp.clone();
>    if (GridUtil.isTimeSequence(tempData)):
>       for t in range(tempData.getDomainSet().getLength()):
>          tempValues = tempData[t]
>          dewptValues = dewptData[t]
>          presValues = presData[t]
>          wetbulbRangeObj = wetbulbData.getSample(t)
>          newValues = wetbulbRangeObj.getFloats(0)
>          print "Processing wetbulb temperature for time ", t
>          for i in range(len(tempValues)):
>             if(str(float(tempValues[i].getValue()))!='nan'):
>                newValues[0][i] =
> findwetbulb(kelvinToCelcius(tempValues[i].getValue()),kelvinToCelcius(dewptValues[i].getValue()),presData[i].getValue())
>          wetbulbRangeObj.setSamples(newValues,1)
>    wetbulbData = newUnit(noUnit(wetbulbData),'Wetbulb temperature in
> celcius','C')
>    return wetbulbData
>
>
> Paul
>
>
>
>
> On 10 December 2013 01:12, Tom Whittaker <whittaker@xxxxxxxx> wrote:
>>
>> Hi Paul --
>>
>> If your function has no logic that needs to be applied to each point,
>> then if the data were read in via the IDV they would be "VisAD Data
>> objects" and you should just be able to do something like:
>>
>> a = b + c - d
>>
>> where "b", "c" and "d" are 3D Data objects (or maybe 4D if they
>> include "time") and it will do the computation on every point. and put
>> the result in "a" (creating a new Data object with characteristics
>> like that of "b" (the first object in the computation).
>>
>> If you have logic, then you might have to iterate over every point...I
>> say "might" because sometimes some of the built-in methods like "mask"
>> can be used to simulate logic.
>>
>> Hope that helps.
>>
>> tom
>>
>>
>>
>> On Sun, Dec 8, 2013 at 9:39 PM, Paul Graham <meteorpaul@xxxxxxxxx> wrote:
>> > Hi IDV'ers,
>> >
>> > I have written a Jython function which takes temperature, dewpoint and
>> > pressure as arguments and evaluated at each point in a 3d domain to
>> > calculate the wet bulb temperature.  What is the best way using Jython
>> > to
>> > iterate over my domain so I can set the wetbulb result for each point?
>> > Eg. wetbulbresult[i][j][k] =
>> > findwetbulb(temperature[i][j][k],dewpoint[i][j][k],pressure[i][j][k]),
>> > where i,j are subscripts for the latitude and longitude and k for the
>> > height.
>> >
>> >
>> > Paul
>> > _______________________________________________
>> > idvusers mailing list
>> > idvusers@xxxxxxxxxxxxxxxx
>> > For list information, to unsubscribe, visit:
>> > http://www.unidata.ucar.edu/mailing_lists/
>>
>>
>>
>> --
>> Tom Whittaker
>> Space Science & Engineering Center (SSEC)
>> Cooperative Institute for Meteorological Satellite Studies (CIMSS)
>> 1225 W. Dayton Street
>> ph: +1 608 262 2759
>
>

--
Tom Whittaker