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Re: Removing equal elements from an array [message #49746 is a reply to message #49744]

Wed, 16 August 2006 08:24

Julio[1]
Messages: 52
Registered: May 2005

Member

Dear Maarten,

I used your code to remove equal elements from an array. It worked fine
for a small array. But I tested using a greater amount of points and
some equal elements (pairs of coords) remains. There are 434 pairs...
an example of them:

234.000 208.000
228.000 208.000
234.000 208.000
234.000 208.000
178.000 209.000
....
153.000 314.000
146.000 318.000
181.000 318.000

The pair (234.000, 208.000) repeats 3 times, so 2 pairs should be
removed. In the output array for these 434 input pairs I have:

234.000 208.000
228.000 208.000
234.000 208.000
178.000 209.000
... and so on

We see the pair (234.000, 208.000) repeats 2 times! Do you have any
idea about what is going on??

Julio

Maarten escreveu:

> Mike wrote:
>> Julio wrote:
>>> I have an array 'A' with two columns, latitudes and longitudes, and
>>> several lines. A need to make another array with the elements of A that
>>> don't repeat.
>>
>> Take a look at the uniq function. Here's an example:
>
> [snip]
>
> Which still doesn't take into account the following situation:
>
> A = [[20.4, 40.3, 50.2, 50.2], $
> [30.2, 60.2, 32.4, 32.5]]
>
> in which case no items should be removed. Just thinking out aloud here.
> With:
> lat = A[*,0] & lon = A[*,1]
>
> we have
> idx_lat = uniq(lat) & idx_lon = uniq(lon)
>
> At the very least both index arrays should be the same, if you want to
> apply this automagically.
>
> If the precision of the coordinates is limited, you can try to combine
> the lat and lon in a single number. If the coordinates are floats, the
> following ought to work:
>
> I = lat + (2.0D0^23)*lon
> idx = uniq(I)
> lat = lat[idx] & lon = lon[idx]
>
> Maarten

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[Message index]

		Re: Removing equal elements from an array By: JD Smith on Wed, 16 August 2006 10:29
		Re: Removing equal elements from an array By: Julio[1] on Wed, 16 August 2006 09:54
		Re: Removing equal elements from an array By: Jean H. on Wed, 16 August 2006 09:12
		Re: Removing equal elements from an array By: Julio[1] on Wed, 16 August 2006 08:24
		Re: Removing equal elements from an array By: Maarten[1] on Wed, 16 August 2006 05:55
		Re: Removing equal elements from an array By: Julio[1] on Wed, 16 August 2006 05:20
		Re: Removing equal elements from an array By: Mike[2] on Tue, 15 August 2006 15:40
		Re: Removing equal elements from an array By: Jean H. on Tue, 15 August 2006 12:14
		Re: Removing equal elements from an array By: Julio[1] on Tue, 15 August 2006 10:36
		Re: Removing equal elements from an array By: Rick Towler on Tue, 15 August 2006 09:30
		Re: Removing equal elements from an array By: JD Smith on Wed, 16 August 2006 10:40

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