Re: Overwriting a value of a variable in a file - and it is written as a different number

On the original file, CO2 was type double (64 bits).

    CO2 = f->CO2 ; double

You created:

CO2 = (/289.263, 289.263, 289.41739141755, 289.579855588959,
289.749383419994,\
  ....
  533.483333333333/) ; float

which is type float (32 bits) which can handle 5-6 decimal places.
All the 'extra' precision is lost (truncated or rounded) to (say)
5 decimal places..

When you did

in->CO2=(/CO2/) ; float into double

you overwrote location reserved for 64-bits with 32 bit values.
It had to fill the spaces with something or, maybe
it used what remained before ... don't know.

Try with the 'd' suffix

O2 = (/289.263d, 289.263d, 289.41739141755d, 289.579855588959d,
289.749383419994d,\
  ....
  533.483333333333d/) ; float

On 10/5/11 2:09 PM, Michael Notaro wrote:
> Try specifying as double.
> Maybe it defaulted as float.
>
>
> On Oct 5, 2011, at 3:06 PM, Madeleine Patterson wrote:
>
>> Hi,
>>
>> I am using the script on
>> http://www.ncl.ucar.edu/Applications/change_netCDF.shtml to overwrite
>> one value of a variable (i.e. just for one year).
>>
>> I change the value of this variable for one year to 478.919898945933,
>> and get the value 478.919891357422 when I check the file for the new
>> value (via ncdump).
>>
>> Similarly, the rest of the values for this variable have changed, e.g.
>>
>> in my script:
>>
>> CO2 = (/289.263, 289.263, 289.41739141755, 289.579855588959,
>> 289.749383419994,\
>> ....
>> 533.483333333333/)
>>
>>
>> But in the ncdump of the altered file (where I changed just one value
>> of this variable):
>>
>> CO2 = 289.263000488281, 289.263000488281, 289.417388916016,
>> ...
>> 533.483337402344, 533.483337402344, 533.483337402344 ;
>>
>> Can anyone tell me what is happening? And how I can fix the script so
>> that the overwritten variable has exactly the same values as the
>> original variable except for the value that my script wants to change?
>>
>> My script is included below...
>>
>> Thanks
>>
>> Madeleine.
>>
>>
>> **********************************************
>> **********************************************
>> begin
>>
>> ; loading libraries
>>
>> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
>>
>> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
>>
>> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
>>
>> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/shea_util.ncl"
>>
>> ;*******************************************************************
>>
>> in = addfile("./ghgfile","w")
>>
>> CO2 = (/289.263, 289.263, 289.41739141755, 289.579855588959,
>> 289.749383419994,\
>>
>> ...
>> 533.483333333333/)
>>
>> in->CO2=(/CO2/)
>>
>> end
>> *****************************************************
>> *****************************************************
>>
>>
>> _______________________________________________
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>
>
>
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Received on Wed Oct 5 14:23:29 2011