[R] Enumerating unit cell traversals Re: Interpolate? a line

[Rainer M Krug]

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On 15/09/10 15:23, David Winsemius wrote:
> 
> On Sep 15, 2010, at 8:58 AM, Rainer M Krug wrote:
> 
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>> On 15/09/10 14:46, Michael Bedward wrote:
>>> Nice posts David. I like the way that 'simple' problems such as this
>>> one give rise to an interesting assortment of approaches and gotchas
>>> :)
>>>
>>> Michael
>>>
>>> On 15 September 2010 22:41, David Winsemius <dwinsemius at comcast.net>
>>> wrote:
>>>>
>>>> On Sep 15, 2010, at 7:55 AM, David Winsemius wrote:
>>>>
>>>>>
>>>>> On Sep 15, 2010, at 7:24 AM, David Winsemius wrote:
>>>>>
>>>>>> Replacing context:
>>>>>>
>>>>>>>> Hello everyone.
>>>>>>>> I have created a 100*100 matrix in R.
>>>>>>>> Let's now say that I have a line that starts from (2,3) point
>>>>>>>> and ends
>>>>>>>> to the
>>>>>>>> (62,34) point. In other words this line starts at cell (2,3) and
>>>>>>>> ends
>>>>>>>> at cell
>>>>>>>> (62,34).
>>>>>>>>
>>>>>>>> Is it possible to get by some R function all the matrix's cells
>>>>>>>> that
>>>>>>>> this line
>>>>>>>> transverses?
>>
>> This is a known problem in computer graphics and the algorythm used to
>> identify these cells is the "Bresenham's Line Drawing Algorithm"
>>
>> You can check out one version at
>>
>> http://www.falloutsoftware.com/tutorials/dd/dd4.htm
>>
>> or
>>
>> http://en.wikipedia.org/wiki/Bresenham's_line_algorithm
> 
> After viewing the Wikipedia description and the illustration I think
> that may not be the same problem. Note that the cells traversed only at
> their very outer corners do not get chosen. The goal is to "approximate
> a line" rather than to enumerate traversals.

You might actually be right.

Cheers,

Rainer
> 


- -- 
Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation
Biology, UCT), Dipl. Phys. (Germany)

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