Search All of the Math Forum:
Views expressed in these public forums are not endorsed by
Drexel University or The Math Forum.
|
|
|
|
Re: How to use "Unique"
Posted:
Nov 12, 2012 12:42 PM
|
|
In article <k7rai0$n1i$1@newscl01ah.mathworks.com>,
"Kevin Ellis" <kevin.ellis86@gmail.com> wrote:
> Hello,
>
> I am having trouble figuring out how to use "unique" to find the index of
> identical elements in a single column cell array. As an example, I have a
> cell array with the following data:
>
> A =
> ''231234242800100043062.68'
> ''231234242800200043208.86'
> ''231234242800400042964.91'
> ''231234242800500038861.19'
> ''231234242800600010255.99'
> ''231234242800900054183.5'
> ''231234242801100077938.9'
> ''231234242801200049682.26'
> ''23123424800900054183.5'
> ''23123424800900054183.5'
> ''23123424GHA0200020256.36'
>
> I have been trying to use unique to find the index of identical elements. In
> this case, the third and second to last values are equal to one another. I
> need to figure out a way to output the indices 9 & 10. I have tried using
> [C1, ia1, ib1] = unique(A,'first'), but still do not understand how "ib1" can
> be used to find the indices 9 & 10.
>
> Also, the order is crucial. The order shown in the example cell array cannot
> change. I realize this may be a question for the help file, but after looking
> at it I still do not fully understand so I am hoping someone could help.
> Thanks.
>
> Kevin
Try this:
[~,~,ib1] = unique(A);
j = find(histc(ib1,1:max(ib1)) > 1);
dupes = find(ismember(ib1,j));
It will find ALL indices of items in A that are duplicated, even if
there is more than one such unique item, i.e., if
A = {'a','a','b','c','c'}
then dupes will be [1 2 4 5];
--
Doug Schwarz
dmschwarz&ieee,org
Make obvious changes to get real email address.
|
|
|
|
