# [ncl-talk] how to get min index within different sequences

Verena Lili verena.prick at gmail.com
Thu Oct 9 13:09:58 MDT 2014

```Hi Mary,

Thanks, would you explain me what exactly the previous error dealing with ?
I did try also to go through this algorithm but not found yet what exactly
the error was.

Thank you,

On Fri, Oct 10, 2014 at 4:00 AM, Mary Haley <haley at ucar.edu> wrote:

> I had an error in my code.  Please see the new code.
>
> I encourage you to learn how to debug this code and understand what's
> going on so you can extend it for your own use.
>
> --Mary
>
>
> On Fri, Oct 3, 2014 at 6:04 AM, Verena Lili <verena.prick at gmail.com>
> wrote:
>
>> Hallo Mary,
>>
>> Im sorry for disturbing you with this email.
>> No solution so far i got to overcome this issue.
>> The algorithmn you suggested is failed once i change the number of
>> sequences.
>>
>> Really look fotward to your help.
>> Best regards,
>>
>> Dr. Verena,
>>
>>
>>
>>
>> On Sunday, September 28, 2014, Verena Lili <verena.prick at gmail.com>
>> wrote:
>>
>>> Hi Mary and NCL,
>>>
>>> The logics still produce errors and are not cosistent once I changed the
>>> number of sequences:
>>> see below my test: I actually only have 5 consecutive series but the
>>> result was 7!
>>>
>>> *x = (/*-999,-999*,9,5,4,6*,-999,-999*,6,5,*-999*,7,*-999
>>> *,25,17,3,2,13,*-999*,-5,*-999*/)*
>>>
>>> x at _FillValue = -999
>>>
>>> nx = dimsizes(x)
>>>
>>> run_inds = new(nx,integer)   ; array to hold minimum indexes of runs
>>> beg_ind = -1                 ; variables to hold begin and end indexes
>>> end_ind = -1                 ; of consecutive sequences of numbers
>>> irun    = 0                  ; counter for number of runs
>>>
>>> ;---Loop through each element and collect groups of runs.
>>> do n=0,nx-1
>>>   if(ismissing(x(n))) then
>>> ;---Check for a run
>>>     if(beg_ind.ne.-1) then
>>>       run_inds(irun) = beg_ind + minind(x(beg_ind:end_ind))
>>>       irun           = irun + 1
>>>       beg_ind        = -1        ; reset back to -1
>>>     end if
>>>     continue
>>>   end if
>>>   if(beg_ind.eq.-1) then
>>> ;---Start a new run
>>>     beg_ind  = n
>>>     end_ind  = n
>>>     prev_ind = n   ; to keep track of consecutive inds
>>>   else
>>> ;---Still in a run
>>>     if((n-prev_ind).eq.1) then
>>>       end_ind = n
>>>     else
>>> ;---End a current run
>>>       run_inds(irun) = beg_ind + minind(x(beg_ind:end_ind))
>>>       irun           = irun + 1
>>>       beg_ind        = -1        ; reset back to -1
>>>     end if
>>>   end if
>>> ;---Special case if on the last number
>>>   if(n.eq.(nx-1).and.beg_ind.ne.-1) then
>>>     run_inds(irun) = beg_ind + minind(x(beg_ind:end_ind))
>>>     irun           = irun + 1
>>>   end if
>>> end do
>>>
>>> print("Number of runs      = " + irun)
>>> print("Min indexes of runs = " + run_inds(0:irun-1))
>>>
>>>
>>> *ncl 43> print("Number of runs      = " + irun)*
>>> *(0) Number of runs      = 7*
>>>
>>> *ncl 44> print("Min indexes of runs = " + run_inds(0:irun-1))*
>>> *(0) Min indexes of runs = 3*
>>> *(1) Min indexes of runs = 5*
>>> *(2) Min indexes of runs = 9*
>>> *(3) Min indexes of runs = 11*
>>> *(4) Min indexes of runs = 14*
>>> *(5) Min indexes of runs = 16*
>>> *(6) Min indexes of runs = 19*
>>>
>>>
>>>
>>> On Mon, Sep 22, 2014 at 12:26 PM, Mary Haley <haley at ucar.edu> wrote:
>>>
>>>> ​Lili,
>>>>
>>>> In the future, please do not post questions to individual developers
>>>> when you don't get a response on ncl-talk.  It's okay to repost to ncl-talk
>>>> after a few days, because we generally try to answer all questions.
>>>>
>>>> You will need to loop through your array and get the start and end
>>>> index of each consecutive sequence of numbers, and then use NCL's minind
>>>> function to get the index of the minimum of this subset, "i =
>>>> minind(x(beg_index:end_index)". There may be a "cleaner" way to do this,
>>>> but this script should work.
>>>>
>>>> See attached script which uses a slightly more complex input array.
>>>>
>>>> --Mary
>>>>
>>>> On Sat, Sep 20, 2014 at 12:55 AM, Verena Lili <verena.prick at gmail.com>
>>>> wrote:
>>>>
>>>>> Hi Mary,
>>>>>
>>>>> I posted this email to ncl talk (see below) and not getting any
>>>>> I've been struggling to figure this out, but not yet get a conclusive
>>>>> result
>>>>>
>>>>> thank you
>>>>>
>>>>>
>>>>> =======================
>>>>> Subject: how to get min index within different sequences
>>>>> To: "ncl-talk at ucar.edu" <ncl-talk at ucar.edu>
>>>>>
>>>>>
>>>>>
>>>>> Hallo,
>>>>>
>>>>> Anyone can suggest how to get the index of the minimum values within
>>>>> different
>>>>> sequences:
>>>>>
>>>>> e.g.:
>>>>>
>>>>>  x = (/-3, -2, -1, 4, 5, 6, 0, -2, 5/)
>>>>>
>>>>>  x at _FillValue=-999
>>>>>  x = where(x.gt.3,x, x at _FillValue)  ; only x>3
>>>>>  print(x)
>>>>>
>>>>> Variable: x
>>>>> (0)     -999
>>>>> (1)     -999
>>>>> (2)     -999
>>>>> (3)     4
>>>>> (4)     5
>>>>> (5)     6
>>>>> (6)     -999
>>>>> (7)     -999
>>>>> (8)     5
>>>>>
>>>>> ; then, how to get *index* pointing the minimum value within these
>>>>> two sequences (3)-(5) and (8),
>>>>> so that the out put will be index:
>>>>>
>>>>> *3 and 8*
>>>>>
>>>>> Thank you.
>>>>>
>>>>>
>>>>> --
>>>>> Regards,
>>>>> Dr. Verena.
>>>>> School of Marine and Atmospheric Sciences
>>>>> Stony Brook University
>>>>> homepage: http://www.somas.stonybrook.edu/
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Regards,
>>>>> Dr. Verena.
>>>>> School of Marine and Atmospheric Sciences
>>>>> Stony Brook University
>>>>> homepage: http://www.somas.stonybrook.edu/
>>>>>
>>>>
>>>>
>>>
>>>
>>> --
>>> Regards,
>>> Dr. Verena.
>>> School of Marine and Atmospheric Sciences
>>> Stony Brook University
>>> homepage: http://www.somas.stonybrook.edu/
>>>
>>
>>
>> --
>> Regards,
>> Dr. Verena.
>> School of Marine and Atmospheric Sciences
>> Stony Brook University
>> homepage: http://www.somas.stonybrook.edu/
>>
>>
>

--
Regards,
Dr. Verena.
School of Marine and Atmospheric Sciences
Stony Brook University
homepage: http://www.somas.stonybrook.edu/
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