On May 1, 12:13 pm, "chenb...@gmail.com" <chenb...@gmail.com> wrote:
> Hello, everyone!
>
> Is there anyone knows a routine in IDL that be capable to remove
> duplicate elements from a multi-dimensional array efficiently? I 'm
> now working with huge arrays, and I have written one by myself, it
> works but is with low efficiency.
>
> example of my problem:
> the input array:
> 1,10,9,100,200
> 2,11,8,101,201
> 2,11,8,101,201
> 3,10,9,100,200
> 4,7,12,99,199
> 2,11,8,101,201
>
> goal:
> remove the duplicate elements with the same values for the second and
> the third column.
>
> expected output:
> 1,10,9,100,200
> 2,11,8,101,201
> 4,7,12,99,199
>
> Thanks for your help!
>
> Bo
How's this:
input = [[1,10,9,100,200],[2,11,8,101,201],[2,11,8,101,201],$
[3,10,9,100,200],[4,7,12,99,199],[2,11,8,101,201]]
; Step 1: Map your columns 2 and 3 into a single unique index
(requires ORD from JBIU):
col2ord = ord(input[1,*])
col3ord = ord(input[2,*])
index = col2ord + (max(col2ord)+1)*col3ord
; Step 2: Use histogram to find which ones have the same unique index
h = histogram(index, reverse_indices=ri)
; Step 3: Get the first one in each bin, and put back in sorted order
keep = ri[ri[where(h gt 0)]]
keep = keep[sort(keep)]
; Step 4: Print them out:
print, input[*,keep]
1 10 9 100 200
2 11 8 101 201
4 7 12 99 199
-Jeremy.
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