Is there a way to initialise an array automatically inside while loop?

Hi all,

I am working on build clustering algorithm (Fixed-width)clustering. In every iteration inside while loop, some points need to be store in an array to use them in final plot. However, I do not know how can I store points that are belonge to a specific cluster in new array in every iteration. The target is showing all points with their clusters in a single plot.

Thank you

Answer 1

[Geoff Hayes]

Abdulatif - if you just want to add some to an array at each iteration of a loop (in your case, a while loop), then you could try the following

 % initialize the cluster points array to be empty
 clusterPoints = [];

 while true

     % do some stuff

     % add (x,y) to clusterPoints
     clusterPoints = [clusterPoints [x;y] ];

 end

In the above, we assume that each point is 2D only. Once we break out of the while loop, clusterPoints will be a 2xm vector where m is the number of points that we have added to the array. The first row will correspond to all x's, and the second row will correspond to all y's.

[Abdulatif Alabdulatif]

Hello Geoff,

The case is I want to assign a group of data points to a new array.

    % f is an original dataset.
    % A is an array that result from clustering function, in my case, I 
     have multiple arrays of (A) that I need to store them in separate 
     arrays to use them in a single plot.

   while true

    [A] = clustring(f);

    % I want to store the array A in another array before move to another
     iteration 
end

I wish it is clear enough now!

Thank you Geoff

[Geoff Hayes]

Hi Abdulatif - try the same above, but use a cell array to capture the the clustered data at each iteration

 % initialize the cluster points array to be empty
 clusterPoints = {};
 atCluster     = 0;

 while true
     % do some stuff

     atCluster                = atCluster + 1;
     clusterPoints{atCluster} = clustring(f);
 end

You could use the same concatenation as the previous example (using the []), but this is just an alternative.

[Abdulatif Alabdulatif]

Hi Geoff,

It is work. However I do not know how I can access to data and use them in plot.

clusterPoints contains: [58x3 double]    [32x3 double]    [1x3 double]    []

How can I use them as numerical data? (Cell array concept is new to me!) : )

Thanks for corporation Geoff

[Geoff Hayes]

If you wish to plot the data by cluster, then you could try

 figure;
 hold all;   % use hold all to plot clusters in different colours
 for k=1:length(clusterPoints)
     data = clusterPoints{k};
     if ~isempty(data)
         plot3(data(:,1),data(:,2),data(:,3),'o');
     end
 end

[Abdulatif Alabdulatif]

Thank you so much!