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Re: Ordered index array [message #45433 is a reply to message #45432]

Thu, 08 September 2005 01:22

Paolo Grigis
Messages: 171
Registered: December 2003

Senior Member

David Fanning wrote:
> David Fanning writes:
>
>
>> How about this:
>>
>> PRO TEST
>> a = [3,6,2,1,2,7,1,1]
>> h = Histogram(a, Reverse_Indices=ri, Min=0)
>> b = Indgen(N_Elements(h)) + 1
>> c = Intarr(N_Elements(h))
>> FOR j=0,N_Elements(h)-1 DO BEGIN
>> IF ri[j+1] NE ri[j] THEN $
>> c[ri[ri[j]:ri[j+1]-1]] = Min(b[ri[ri[j]:ri[j+1]-1]])
>> ENDFOR
>> Print, c
>> END
>>
>> 1 2 3 4 3 6 4 4
>>
>> Note that your original example is wrong. :-)
>
>
> Whoops! *I* didn't use the original example either (although
> yours is still wrong!).
>
> Here is a more complete solution, using the original data:
>
> PRO TEST
> a = [3,6,2,1,2,8,1,1]
> h = Histogram(a, Reverse_Indices=ri, Min=0)
> b = Indgen(N_Elements(h)) + 1
> c = Intarr(N_Elements(h))
> FOR j=0,N_Elements(h)-1 DO BEGIN
> IF ri[j+1] NE ri[j] THEN $
> c[ri[ri[j]:ri[j+1]-1]] = Min(b[ri[ri[j]:ri[j+1]-1]])
> ENDFOR
> Print, c[0:N_Elements(a)-1]
> END
But this will fail if 'a' has more elements than the number of
its different values, for instance a=[3,3,1,2,3,2,2,1,2,3].

One could try this:

PRO test

a=[3,3,1,2,3,2,2,1,2,3]

b=a
c=intarr(n_elements(a))

h=histogram(a,min=1,reverse_ind=ri)

done=0
rank=1
WHILE NOT done DO BEGIN
actual_value=b[0]
ind_actual_value=ri[ri[actual_value-1]:ri[actual_value]-1]
c[ind_actual_value]=rank
rank=rank+1
indremove=where(b NE actual_value,count)
IF count GT 0 THEN b=b[indremove] ELSE done=1
ENDWHILE

print,a
print,c

END

but it will get inefficient as the numbers of different values
in 'a' grows, as the code in the loop get called more and more
times...

Ciao,
Paolo

>
> Cheers,
>
> David
>
>

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[Message index]

		Re: Ordered index array By: Emmanuel Christophe on Thu, 08 September 2005 07:51
		Re: Ordered index array By: David Fanning on Thu, 08 September 2005 06:55
		Re: Ordered index array By: Paolo Grigis on Thu, 08 September 2005 06:51
		Re: Ordered index array By: David Fanning on Thu, 08 September 2005 06:08
		Re: Ordered index array By: David Fanning on Thu, 08 September 2005 06:02
		Re: Ordered index array By: Paolo Grigis on Thu, 08 September 2005 05:30
		Re: Ordered index array By: Paolo Grigis on Thu, 08 September 2005 03:03
		Re: Ordered index array By: Emmanuel Christophe on Thu, 08 September 2005 01:58
		Re: Ordered index array By: Emmanuel Christophe on Thu, 08 September 2005 01:48
		Re: Ordered index array By: Paolo Grigis on Thu, 08 September 2005 01:22
		Re: Ordered index array By: David Fanning on Wed, 07 September 2005 10:17
		Re: Ordered index array By: David Fanning on Wed, 07 September 2005 10:01

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