Looping/Conditional statements when I don't know the exact end point

Hello,

I have an array that contains multiple points in 3D space. These points have been grouped into clusters based on their proximity to one another. The number of clusters aren't always constant. There could be multiple or no clusters in a set of data(i.e. clusters or just individual points). I need to plot these points on a 3D graph and assign colours based on the cluster(i.e. one specific coulr per cluster) and one cluster for lone points. The array works in the following way:

Columns 1,2,3 : X,Y,Z coordinates

Column 4: Cluster number that point has been assigned to (-1 for individual point and 1,2,3 etc. for that cluster, 0 does not exist)

Since I do not know how many clusters exist in the data set to begin with (I find it out later), how can I assign individual colors when I do not know how many I will need?

I have tried in the following way, but I think there has to be a better way to do this. My method visits each point multiple times based on how many clusters exist. Is there a better way that only visits each point once?

Thanks for any help.

Pranav

for i=-1:1:numofClusters
    for j=1:rows
        if targetinfo(j,4)==i
            if i==-1
                scatter3(targetinfo(j,1),targetinfo(j,2),targetinfo(j,3)...
                ,'k' ,'*')   %noise
            else
                scatter3(targetinfo(j,1),targetinfo(j,2),targetinfo(j,3)...
                ,cm(i,:),'o')  %point in cluster
            end
        end
    end
end