multiple convex hull clusters to plot in a single figure

My data has 3 columns.. x (x axis data), y (y axis data) and z (cluster number). Each cluster has more than 3 points and they are all in order.

Here is how the data looks:

I want to be able to apply a convex hull for each set of clusters and then plot the entire result together. My code is unable to do that instead it is throwing up a figure (see below)

[ndata, text, alldata] =  xlsread(fullfile(source_dir));

     [~, y] = sort(ndata(:,end));
     As = ndata(y,:);

     lon = As(:,1); 
     lat = As(:,2);
     cluster = As(:,3);

     %%To find number of points in a cluster (repetitions)
     rep = zeros(size(cluster));

     for j = 1:length(cluster)
         rep(j) = sum(cluster==cluster(j));
     end

     %%Less than 3 points in a cluster are filtered out

     x = lon (rep>3);
     y = lat (rep>3);
     z = cluster (rep>3);

     %%convex hull for each cluster plotted ....hold....then display all.

     figure
     hold on

     clusters = unique(z);

         for i = 1:size(z)

            k=convhull(x( z == clusters(i)), y( z == clusters(i)));

            plot(x, y, 'b.'); %# plot cluster points
            plot(x(k),y(k),'r-'); %# plots only k indices, giving the convex hull

         end

Please could someone help me! Thank you very much, I really appreciate your help...........

Answer 1

[Matt J]

I don't fully understand what you're trying to do, but it sounds like the PATCH command would be better suited than PLOT.