Re: [idvusers] Adding two different 4d grids

Hi Paul-

On 8/27/13 4:26 PM, Paul Graham wrote:
Hi Don,

The first method generates a "visad.UnitException".  The second one (with
noUnit) generates "java.lang.NullPointerException".  Any ideas as to what
can be done?

I suggest running your second method and when the error occurs, use the submit button to submit this to Unidata support. That will provide them with the stack trace so they can track down the problem. In theory, it should work. ;-)

I would expect the unit exception from the first method. Unlike most other programs which ignore units, IDV will try to do automatic unit conversion between variables. That way you can add temperatures in Celsius to temperatures in Kelvin and get a meaningful answer. In the real world, you can't physically add quantities with incompatible units and get a meaningful answer (e.g. you can't get a valid unit result out of adding a gallon to a meter). But here you just want to add some numbers together, so making the IDV ignore units with the noUnit method is the way to go.

Don

On 28 August 2013 08:25, Paul Graham <meteorpaul@xxxxxxxxx> wrote:

Hi Don,

The first method generates a "visad.UnitException".  The second one (with
noUnit) generates "java.lang.NullPointerException".  Any ideas as to what
can be done?

Thanks,

Paul


On 27 August 2013 23:19, Don Murray (NOAA Affiliate) <don.murray@xxxxxxxx>wrote:

I would expect that the second one would work.  What errors do you get?

Don


On 8/26/13 8:49 PM, Paul Graham wrote:

Dear IDV Users,

What is the best way to add two different 4d grids (ie. having different
units) in order to create dimensionless field?

Eg.  Suppose, for whatever reason, you wanted to add convective available
potential energy (CAPE), F1, and rainfall rate, F2.

I have not been able to get either of the following to work (IDV produces
errors):

def simpleAdd(F1,F2):
    res = add(F1,F2)
    return res

def simpleAdd(F1,F2):
    res = add(noUnit(F1),noUnit(F2))
    return res

What should I do?

Thanks,

Paul
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Don Murray
NOAA/ESRL/PSD and CIRES
303-497-3596
http://www.esrl.noaa.gov/psd/people/don.murray/