MATLAB: Help with plot legend

MATLABplot scatter loop legendStatistics and Machine Learning Toolbox

I am trying to plot several groups (25 in my example) of data on one plot, with a legend representing each. Here is my code:
 aa = 25;
 c = hsv(n);
 n = 25
 figure; hold on; axis tight; grid on; box on;
 for k = 1:n;
    xy = c(k,:);  % assign a different color to each group
a = outputs2{1,k} % my data is held in cells in a 1 x 25 cell array
if sum(a) ~= 0; % some groups of data are empty (this data was generated from the nctool
    h(k) = scatter(a(:,3), a(:,1), aa, xy, 'filled') % seems to work....
    name{k} = ['group ' num2str(k)]; % attempting to make a string array for the legend
end
 end 
 legend(h, name);
But i get this error:
 Error using legend (line 120)
 Invalid argument. Type 'help legend' for more information.
 Error in PlotOutputs2 (line 19)
 legend(h, name);
 Error in run (line 96)
 evalin('caller', [script ';']);
The plot works, just not the legend. I've tried a hundred different variations and this is the closest i can get.
Also, and this is a different problem, but i spent some time trying to install the legappend tool this morning with no luck. That was also error prone. With that, i ran the example that comes with it and just got errors. I'm not sure what the mistake I'm making with that is.
Also today I reinstalled MATLAB just in case I had damaged the legend tool somehow.
Any help is greatly appreciated!!!!

Best Answer

Not very sure, but I guess that the problem might be in some of the elements of h being zero, on account of the condition about empty plots.
May I suggest this? Just plot what you have to plot, and use the DisplayName property to set the relevant legend string
 name = ['group ' num2str(k)];
 h(k) = scatter(a(:,3), a(:,1), aa, xy, 'filled','DisplayName',name);
After you're done, inserting the legend
 legend(gca,'show');
should show the correct thing.
Otherwise, you may modify your code so that h contains only entries corresponding to existing objects. You can find nonzero elements in h, or introduce a different counter kk that is increment only for nonempty groups...
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