MATLAB legend() Function in for-loop- add entry in every loop

Question

i have searched a lot but i did not manage to create a for-loop, or something similar in order to add an extra entry in the legend area in every loop. For example: 1st loop- 1 entry in the legend 2nd loop- 2 entries in the legend... i have tried the legappend function but i get errors, even with examples that are provided. Below you can see a section of my code:

    Eb_N0_dB = [-10:25];        
    k_dB=[-inf 10 20];             
    figure(1)
    hold on
    semilogy(Eb_N0_dB,simBer);
    legend(sprintf('sim (nTx=2, nRx=2 k=%d, Alamouti)',k_dB(1)))
    legend boxoff

    for qq=2:length(k_dB)
    legappend(sprintf('sim (nTx=2, nRx=2 k=%d, Alamouti)',k_dB(qq)))
    end

   %%simBer is a {length(k_dB),length(Eb_N0_dB)} matrix

i get the error below

    Error using legend (line 120)
    Invalid argument. Type 'help legend' for more information.

    Error in legappend (line 74)
    [legend_h,object_h,plot_h,text_strings] = legend(h,allDatah,str);

Any suggestions? Regards

It may be worth noting that legappend is not part of the standard MATLAB library and you have to get it through FEX: mathworks.com/matlabcentral/fileexchange/47228-legappend — rayryeng

anon01 anon01 · Accepted Answer · 2015-08-27T21:06:14

I create an empty variable and then add cell array elements of strings for each legend entry. Appending a legend entry at the point in code where you add a plot is a convenient way to keep things organized - otherwise you may have blank or doubled legend entires:

x = 1:4;
figure
hold all

L ='';
%L = cell(1,N);

for j = 1:length(x)

    scatter(j,x(j),60,'filled');
    L = [L,{num2str(j)}];

end

%additional plots are easily added or taken out, leaving the legend in tact:
scatter(rand,rand,90,'x','linewidth',3);
L = [L,'optional data a'];

scatter(rand,rand,90,'x','linewidth',3);
L = [L,'optional data b'];

legend(L);

MATLAB legend() Function in for-loop- add entry in every loop

1 Answers