matlab, symbol not updating in legend - matlab

Question

I am creating a program where the user can select multiple files to plot and compare data. The program can properly graph the data, the problem I have encountered is within the legend.
I tried posting an image, however I do not have a high enough reputation. So I will try to explain the graph in detail. Two sets of points are plotted (two matrices of different sizes). The curves are labeled by the user, and in this example they are: "PS, Cs" and "PS, Po."
The program successfully plots the "PS, Cs" curve with the red squares then plots the "PS, Po" with the blue circles however the legend continues to show the red squares for both sets of points. Below is the loop within the code that does the plotting.
fig = small_group_struct;
mystyles = {'bo','rs','go'};
mat_len = size(small_group_struct,2);
for q = 1:mat_len
plotstyle = mystyles{mod(q,mat_len)+1};
semilogy(1:size(small_group_struct(1).values),small_group_struct(q).values,plotstyle);
hold all;
[~,~,~,current_entries] = legend;
legend([current_entries {small_group_struct(q).name}]);
end
hold off;
%legend(small_group_struct.values,{small_group_struct.name});
Other threads that I have seen suggested putting the plot command into a handle but since each set of points is a nxm matrix of different sizes, the program does not like this.
Also, as mentioned at the beginning the user will select the number of files and while this is typically two, it will not always be the case and why I am trying to plot it within a for loop.
Any suggestions and comments would be greatly appreciated.
EDIT: I now have a high enough reputation to post images, so here is a screenshot of the graph

Answer 1

You can use handles to specify what labels go with what data in the legend.
You say that "each set of points is a nxm matrix of different sizes." Plotting an mxn matrix creates n line objects and returns n handles. You can keep track of all of these handles and assign labels to them when you create the legend.
Here's an example:
% Cell array of data. Each element is a different size.
data = {rand(100, 1), rand(150, 2)};
styles = {'ro', 'gs'};
% Vector to store the handles to the line objects in.
h = [];
figure
hold on
for t = 1:length(data)
% plots the data and stores the handle or handles to the line object.
h = [h; semilogx(data{t}, styles{t})];
end
% There are three strings in the legend because a total of three columns of data are
% plotted. One column of data is from the first element of data, two columns of data
% are from the second element of data.
strings = {'data1' ,'data2', 'data3'};
legend(h,strings)
You might want to do something different with the legend but hopefully this will get you started.