Re: regarding the retention of coordinate variables

From: <shea_at_nyahnyahspammersnyahnyah>
Date: Mon Aug 19 2013 - 22:04:26 MDT

Also ... If you think an equation

    A = B*C/Q + 5.2 +linint2(.....) + (T/conform(T,1,p))^0.286

What meta data is appropriate? In particular, what attributes would you
associate with variable 'A'

long_name? units?
Consider that B, C, Q, T, p may have attributes that are appropriate
for that variable but not to the result 'A'

Coordinates? Q may have coordinate variables but maybe B and C don't.
Further, T may have coordinates but with different names?
How is NCL to unravel this situation?

The only attribute handle automatically is _FillValue. In the above,
'A'will get the _FillValue assigned the the 1st variable encountered
(Here, B)

> Hi Danny,
>
> This is a good question.
>
> Copying over coordinate data and/or attributes can be an expensive
> operation, both time-wise and memory-wise, especially if you have large
> arrays and/or lots of arrays.
>
> I believe it was a conscious decision when NCL was first being developed
> to have this NOT be the default behavior, and to let the user manage this.
>
> We do provide special _Wrap versions of some functions which copy over
> meta data, but unfortunately not for the ones that you listed.
>
> It may not be very hard to add your own _Wrap versions of the functions
> you listed.
>
> Look at the fie:
>
> $NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl
>
> and search for "_Wrap ("
>
> You will see that all of these functions have corresponding "_Wrap"
> versions that work exactly the same as their non-_Wrap counterparts,
> except they add metadata:
>
> area_conserve_remap_Wrap
> area_hi2lores_Wrap
> cssgrid_Wrap
> dim_avg_Wrap
> dim_avg_n_Wrap
> dim_avg_wgt_Wrap
> dim_avg_wgt_n_Wrap
> dim_cumsum_Wrap
> dim_cumsum_n_Wrap
> dim_max_n_Wrap
> dim_min_n_Wrap
> dim_rmsd_Wrap
> dim_rmsd_n_Wrap
> dim_rmvmean_Wrap
> dim_rmvmean_n_Wrap
> dim_rmvmed_Wrap
> dim_rmvmed_n_Wrap
> dim_standardize_Wrap
> dim_standardize_n_Wrap
> dim_stddev_Wrap
> dim_stddev_n_Wrap
> dim_sum_Wrap
> dim_sum_n_Wrap
> dim_sum_wgt_Wrap
> dim_sum_wgt_n_Wrap
> dim_variance_Wrap
> dim_variance_n_Wrap
> dv2uvF_Wrap
> dv2uvG_Wrap
> eofcor_Wrap
> eofcor_pcmsg_Wrap
> eofcor_ts_Wrap
> eofcov_Wrap
> eofcov_pcmsg_Wrap
> eofcov_ts_Wrap
> eofunc_Wrap
> eofunc_ts_Wrap
> eofunc_varimax_Wrap
> f2fosh_Wrap
> f2foshv_Wrap
> f2fsh_Wrap
> f2fshv_Wrap
> f2gsh_Wrap
> f2gshv_Wrap
> fo2fsh_Wrap
> fo2fshv_Wrap
> g2fsh_Wrap
> g2fshv_Wrap
> g2gsh_Wrap
> g2gshv_Wrap
> ilapsF_Wrap
> ilapsG_Wrap
> int2p_Wrap
> int2p_n_Wrap
> linint1_Wrap
> linint1_n_Wrap
> linint2_Wrap
> natgrid_Wrap
> obj_anal_ic_Wrap
> rcm2rgrid_Wrap
> rgrid2rcm_Wrap
> shsgc_R42_Wrap
> triple2grid_Wrap
> uv2dvF_Wrap
> uv2dvG_Wrap
> uv2vrF_Wrap
> uv2vrG_Wrap
> vr2uvF_Wrap
> vr2uvG_Wrap
> wgt_areaave_Wrap
> zonal_mpsi_Wrap
>
> You might be able to use one of these as a template for adding your own
> _Wrap versions of the functions you enquired about.
>
> --Mary
>
> On Aug 19, 2013, at 3:17 PM, Daniel Barandiaran <dbarandiaran@gmail.com>
> wrote:
>
>> Hi NCLers,
>>
>> This question is specifically for the developers. In my work I make
>> frequent use for functions such as escorc, regCoef,
>> center_finite_diff_n, and I am sure there are others for which my
>> problem is applicable, but they slip my mind at the moment. Anyway, my
>> question is this: these functions do not retain the coordinate variables
>> in the output; why not? I am sure there is a reason for this, and I am
>> also well-aware of tricks like copy_VarCoords, or pre-assigning the
>> variable name in such a way that coordinate variables are assigned
>> before the desired function is used, but this adds lines to my code. I
>> have been on a quest, if you will, to make my codes shorter and sleeker,
>> and this is a frequent thorn in my side. Maybe I am being too
>> nit-picky, and I have no doubt that you all have more pressing things on
>> your plate than to satisfy the desires of my quest for short code, but I
>> am curious as to why this wasn't worked into functions such as this in
>> the first place. No hur
> ry on this one, and as always I greatly appreciate all the work you guys
> do for all of us NCL users.
>>
>> --
>> Danny Barandiaran
>> Department of Plants, Soils, and Climate
>> Utah State University
>>
>>
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Received on Mon Aug 19 22:04:36 2013

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