Prev: Problem about controlling Pan and tilt of Logitech Orbit webcam
Next: adjecent
From: leo nidas on 4 Jun 2010 12:10

Hi there,

I want to do something simple but turned out to be a headache for me.

I have the array for example a=[2 5 5 8 8 8 9 16 16 20];
I want to come up with array b=[1 2 2 3 3 3 4 5 5 6];

I think it is clear.
Array a will always be sorted with positive integers. Array b will be sorted too,with positive integers, but the maximum difference will be 1. Array b will always begin from 1.

I tried working with an if inside a for and the diff function but I failed big time, I assume that a simpler way may exist.

Thanx in advance for any anwers!
From: Jeremy on 4 Jun 2010 12:28
This should do it:

a=[2 5 5 8 8 8 9 16 16 20];

index = 1;
b(1) = 1;
for i = 2:size(a,2)
if a(i) ~= a(i-1)
index = index + 1;
b(i) = index;
else
b(i) = index;
end
end
From: dpb on 4 Jun 2010 12:31
leo nidas wrote:
>
> Hi there,
>
> I want to do something simple but turned out to be a headache for me.
>
> I have the array for example a=[2 5 5 8 8 8 9 16 16 20];
> I want to come up with array b=[1 2 2 3 3 3 4 5 5 6];
>
> I think it is clear. Array a will always be sorted with positive
> integers. Array b will be sorted too,with positive integers, but the
> maximum difference will be 1. Array b will always begin from 1.
>
> I tried working with an if inside a for and the diff function but I
> failed big time, I assume that a simpler way may exist.

....

>> u=unique(a);
>> [n,bin]=histc(a,u)
n =
1 2 3 1 2 1
bin =
1 2 2 3 3 3 4 5 5 6
>>

--
From: Doug Schwarz on 4 Jun 2010 13:17
leo nidas wrote:
>
> I have the array for example a=[2 5 5 8 8 8 9 16 16 20];
> I want to come up with array b=[1 2 2 3 3 3 4 5 5 6];

[unused,unused,b] = unique(a);

--
Doug Schwarz
dmschwarz&ieee,org
Make obvious changes to get real email address.
From: Bruno Luong on 4 Jun 2010 13:42
HISTC, UNIQUE solutions will call for some kind of sorting, which can be penalizing for large array. Jeremy's for-loop solution has better theoretical complexity, but it's not vectorized. Another solution is:

b = cumsum([1 diff(a)>0])

Bruno
 |  Next  |  Last
Pages: 1 2
Prev: Problem about controlling Pan and tilt of Logitech Orbit webcam
Next: adjecent