Hi all,
Thanks for this most instructive help.
Good to have you people around.
Thomas
Dick Jackson schrieb:
> Hi all,
>
> "Ben Tupper" <btupper@bigelow.org> wrote in message
> news:43d48fF1n6d7qU1@individual.net...
>
>> Thomas Pfaff wrote:
>
>
>>> [...] how can I transform an array
>>> like this
>>>
>>> series = [1,1,0,0,0,0,1,0,1,1,1,0,0,1,1]
>>>
>>> into something like this
>>>
>>> durations = [2,1,3,2]
>>>
>>> which is I want to count all contiguous fields of '1's in an array.
>
>
>> I think I would use a combination of LABEL_REGION and HISTOGRAM.
>>
>>
>> ****START
>> series = [1,1,0,0,0,0,1,0,1,1,1,0,0,1,1]
>>
>> nSeries= n_elements(Series)
>>
>> buffered = [0,series,0]
>> dummy = FIX(LABEL_REGION(buffered))
>> label = dummy[1:nSeries]
>>
>> H = HISTOGRAM(label, MIN = 1S)
>>
>> print, series
>> print, label
>> print, H
>> *****END
>>
>>
>> Note the you must pad series with "background" values at the endpoints.
>
>
> I have to say, that looks pretty cool, as requested! I've approached this
> another way, playing from Ben's 'buffered' array, finding where we have
> transitions from 0->1 or 1->0:
>
> ; Find where all transitions occur
> whereChange = Where(buffered[1:*] NE buffered, nChange)
>
> ; Change array to [2, m]
> whereChange = Reform(whereChange, 2, nChange/2, /Overwrite)
>
> ; Measure distance from odd transitions to even transitions
> durations = Reform(whereChange[1, *] - whereChange[0, *])
>
> In case anyone would want to know the time or memory efficiency of these (I
> was curious), I tried to optimize them as much as possible and put them
> through their paces with long series:
>
> =====
>
> PRO TimeSeriesDurations, n
>
> ;series = [1,1,0,0,0,0,1,0,1,1,1,0,0,1,1]
>
> IF N_Elements(n) EQ 0 THEN n = 1E6
> series = RandomU(seed, n) GT 0.5
>
> nSeries= n_elements(Series)
>
> buffered = [0,series,0]
>
> ; DJ method:
>
> m0 = Memory(/Current)
> t0 = SysTime(/Seconds)
>
> whereChange = Where(buffered[1:*] NE buffered, nChange)
> IF nChange EQ 0 THEN Return ; No 1's in series
> whereChange = Reform(whereChange, 2, nChange/2, /Overwrite)
>
> durations = Reform(whereChange[1, *] - whereChange[0, *])
>
> Print, 'DJ time: ', SysTime(/Seconds)-t0
> Print, 'DJ memory: ', Memory(/Current)-m0
>
> ; BT method:
>
> m0 = Memory(/Current)
> t0 = SysTime(/Seconds)
>
> ; Need to use ULong for longer series:
> ;dummy = LABEL_REGION(buffered, /ULong)
> ;label = dummy[1:nSeries]
> ; Compressed to this for efficiency:
> label = (LABEL_REGION(buffered, /ULong))[1:nSeries]
>
> H = HISTOGRAM(label, MIN = 1S)
>
> Print, 'BT time: ', SysTime(/Seconds)-t0
> Print, 'BT memory: ', Memory(/Current)-m0
>
> Print, 'Differing results: ', Total(durations NE H)
>
> END
>
> =====
>
> Running this gives:
>
> IDL> timeseriesdurations,1E6
> DJ time: 0.030999899
> DJ memory: 3003060
> BT time: 0.062000036
> BT memory: 5001132
> Differing results: 0.000000
>
> IDL> TimeSeriesDurations,1E7
> DJ time: 0.39000010
> DJ memory: 30011760
> BT time: 0.51600003
> BT memory: 50004032
> Differing results: 0.000000
>
> Any other methods out there? Hope this helps!
>
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