How do I replace this for-loop?

[Martin Weiser]

On Sat, 5 Jul 2008, Martin Weiser wrote:

> On Fri, 4 Jul 2008, Robert Macy wrote:
>
>> What's the best way to replace this for-loop?
>>
>> Given an array, n, of datapoints, such that:
>>
>>>> size(n)
>> rows = 27000
>> columns = 2
>>
>> where n(:,1) are all the integer x values, and
>> n(:,2) are all the integer y values,
>> both integer values are in the range of 1 to 101
>>
>> I slowly did it this way:
>>
>> output=zeros(101,101);
>> for i=1:27000
>>  output( n(i,1),n(i,2) ) = output( n(i,1),n(i,2) ) + 1;
>> endfor
>>
>> as you all know this is fairly slow.
>> What's a simple way to replace this for-loop?
>>
>> Robert
>>
> Hi,
> what about something like:
> ni=zeros(27000,1);
> ni=sub2ind(size(n),n(:,1),n(:,2));
> ni=sort(ni);
> [breaks,garbage,indeces]=find(ni-shift(ni,1);
> times=breaks-shift(breaks,1);
> output=zeros(101,101);
> output(indeces)=times;
>
> (I would guess that people here will come with something much more
> straightforward and elegant, maybe with an one-liner.)
> I have not tested that, but HTH
> Martin W.

Hello,
I am sorry, I have realized now that I was almost completely wrong.
Sorry again,
Martin W. 
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