Re: Problems extracting run from dim_numrun using dim_sum

Hi Dominique,
x = dim_numrun_n(cold_mn, 1, 0) ; cold_mn = time x lat x lon

For the above syntax, dum_numrun_n will return the number of /unique/
runs present at each lat lon point. Take a look at example #2 here:
http://www.ncl.ucar.edu/Document/Functions/Built-in/dim_numrun_n.shtml

x(0,:,:) will contain the number of instances at each lat/lon point
where the run length = 1.
x(1,:,:) will contain the number of instances at each lat/lon point
where the run length = 2.
and so on.

So, if you want to see the number of instances of run length 5 at 40N,
5E, you can do this:
print(x(4,{40},{5}))

The following syntax will put the same input in every instance
ofspell_tot_unique_mn, because the right hand side of the equation is
not changing with every iteration of nr.
do nr=0,nspell-1
spell_tot_unique_mn(nr,:,:) = dim_sum_n(cold_mn1,0)

end do

I'm not sure if I'm right or not, but after reading your email I don't
think you need to use dim_sum_n at all, and just use the output from
dim_numrun_n as that returns the number of unique runs for each run
length at each grid point. If I am incorrect in my line of thinking
here, please respond back to ncl-talk further describing what you are
trying to accomplish. Adam

On 10/2/12 12:24 PM, Cannavina, Dominique wrote:
>
> Hi NCL Talk
>
> I have extracted a daily minimum temperature (t2_mn) for consecutive
> years from a data set over a specified area (lat, lon).
>
> dim_numrun_n was used to find the number of cold spells (i.e. number
> of consecutive cold spells of 1 day, 2 days....20 days etc
>
> tcrit = 0 ; specify cut off temperature 'tcrit'
>
> cold_mn = where(t2_mn.le.tcrit, 1, 0) ;create 0/1 array
>
> cold_mn1 = dim_numrun_n(cold_mn, 1, 0) ; opt = 0 means total
> (time,lat,lon)
>
> .
>
> .
>
> .
>
> Variable: cold_mn1
>
> Type: integer
>
> Total Size: 67145680 bytes
>
> 16786420 values
>
> Number of Dimensions: 3
>
> Dimensions and sizes: [run_length | 12235] x [lat | 28] x [lon | 49]
>
> Coordinates:
>
> run_length: [1..12235]
>
> lat: [73.5..33]
>
> lon: [-27..45]
>
> Number Of Attributes: 2
>
> cold_crit_values : 0
>
> long_name : unique cold runs
>
> Then dim_sum_n was used to extract the number of 1 day, 2 day spells
> at each lat,lon
>
> This is the bit I am having problems with
>
> I initially had the following line in the do loop below, but the
> subscripting is unbalanced so it rightly won't work
>
> spell_tot_unique_mn(nr,:,:) = dim_sum_n(cold_mn1({spell(nr)},:,:),0)
>
> .
>
> .
>
> .
>
> So I removed the subscripting which gave me the following do loop,
> which although it didn't return any erro, when I went to plot the
> data, it returns the same set of values for each spell duration or 'nr'
>
> ; Set range for spell
>
> n1 = 1
>
> n2 = 100 ; ispan to specify all spells
>
> spell = ispan(n1,n2,1) ; eg n1=1, n2=20
>
> nspell = dimsizes(spell)
>
> ; Select out 'unique runs'
>
> do nr=0,nspell-1
>
> spell_tot_unique_mn(nr,:,:) = dim_sum_n(cold_mn1,0)
>
> end do
>
> spell_tot_unique_mn!0 = "spell"
>
> spell_tot_unique_mn&spell = spell
>
> copy_VarCoords(cold_mn1(0,:,:), spell_tot_unique_mn(0,:,:)) ; trick
> for coords
>
> printVarSummary(spell_tot_unique_mn)
>
> print(dimsizes(spell))
>
> printMinMax(spell_tot_unique_mn,True)
>
> Variable: spell_tot_unique_mn
>
> Type: float
>
> Total Size: 548800 bytes
>
> 137200 values
>
> Number of Dimensions: 3
>
> Dimensions and sizes: [spell | 100] x [lat | 28] x [lon | 49]
>
> Coordinates:
>
> spell: [1..100]
>
> lat: [73.5..33]
>
> lon: [-27..45]
>
> Number Of Attributes: 2
>
> spell : 1
>
> _FillValue : 9.96921e+36
>
> (0) 100
>
> (0)
>
> (0) min=0 max=976
>
> So I think although the dim_sum_n is summing run length from coldmn1,
> it is not differentiating between a 1 day run, 2 day run etc?
>
> The full script and all the associated variables are attached in two file.
>
> How can I get the dim_sum_n to sum the 'correct' spell lengths?
>
> Any help much appreciated.
>
> Kind regards
>
> Dominique
>
>
>
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Received on Tue Oct 2 16:16:06 2012