Hi Valentin,
Thanks a lot for your suggestion! It makes exactly what I need, with a
clear code. I still don't know if efficiency will be an issue for my
problems, but I hope it won't.
Just don't agree with your advice to only post in one place. Is there any
special reason for it besides the overlap of users?
I see some differences between asking in the mailing-list or in
stackoverflow, even if there is an overlap between of users of both forums.
In stackoverflow there is kind of a competition of the best responses that
I think is interesting, we can learn a lot from everyone there. And I think
it is not the focus of this list. Just my opinion.
By the way, the final solution for my problem is the following piece of
code:
using Images
function findMat(mat,value)
return(collect(zip(ind2sub(size(mat),find( x -> x == value, mat))...)));
end
mat = [1 1 0 0 0 ; 1 1 0 0 0 ; 0 0 0 0 1 ; 0 0 0 1 1]
labels = label_components(mat);
for c in 1:maximum(labels)
comp = findMat(labels,c);
println("Component $c is composed by the following elements
(row,col)");
println("$comp\n");
end
Thanks again for your help!
Best,
Charles
On 25 September 2015 at 09:07, Valentin Churavy <v.chur...@gmail.com> wrote:
> Hej Charles,
>
> in the future please only post in one place. A lot of the people who
> answer on SO are also here.
>
> You can use the label_components function in Images.jl
> https://github.com/timholy/Images.jl/blob/master/doc/function_reference.md#label_components
> To get the the list of coordinates for each components you then would have
> to do something along the line of.
>
> for c in 1:maximum(labels)
> find(x-> x == c, labels)
> end
>
> Not very efficient but that should get you started.
>
> On Friday, 25 September 2015 07:56:20 UTC+9, Charles Santana wrote:
>>
>> Assume I have the following matrix:
>>
>> mat = [1 1 0 0 0 ; 1 1 0 0 0 ; 0 0 0 0 1 ; 0 0 0 1 1]
>>
>> Considering as a "component" a group of neighbour elements that have
>> value '1', how to identify that this matrix has 2 components and which
>> vertices compose each one?
>>
>> For the matrix *mat* above I would like to find the following result:
>>
>> Component 1 is composed by the following elements of the matrix
>> (row,column):
>>
>> (1,1)
>> (1,2)
>> (2,1)
>> (2,2)
>>
>> Component 2 is composed by the following elements:
>>
>> (3,5)
>> (4,4)
>> (4,5)
>>
>> I can use Graph algorithms like this
>> <http://graphsjl-docs.readthedocs.org/en/latest/algorithms.html#connected-components>
>> to identify components in square matrices. However such algorithms can not
>> be used for non-square matrices like the one I present here.
>>
>> Any idea will be much appreciated.
>>
>> I am open if your suggestion involves the use of a Python library +
>> PyCall for example. Although I would prefer to use a pure Julia solution.
>>
>> Regards
>> Charles
>> P.S.: Just asked the same question in Stackoverflow:
>> https://stackoverflow.com/questions/32772190/how-to-find-connected-components-in-a-matrix-using-julia
>>
>> --
>> Um axé! :)
>>
>> --
>> Charles Novaes de Santana, PhD
>> http://www.imedea.uib-csic.es/~charles
>>
>
--
Um axé! :)
--
Charles Novaes de Santana, PhD
http://www.imedea.uib-csic.es/~charles
