I am getting Warning: Ignoring extra legend entries

% T represents Temperature in Kelvin,K
% mu represnt Viscosity

%downloading the ascii data file

Data = importdata('viscosity_data.dat');
T= Data(1,:);
mu= Data(2,:);   

% to return the no.of elements n1 & n2 in arrays of T & mu
n1=numel(T);
n2=numel(mu);
i=0; % dependent variable, changing w/change in temp. 

if n1==n2

K=input('Enter Temperature,K at which to estimate Viscosity: ');
    if K>=T(1) && K<=T(n1)
% for loop         
        for m=1:n1
            if T(m)==K;
                i=mu(m);
            end %end if 6
            if(i==0)

                      if (K<=T(m) && K>=T(m-1))
            % applying the variable into linear interpolation equation              
                          i=(mu(m)-mu(m-1))/(T(m)-T(m-1))*(K-T(m)+mu(m));
                      end %end if 5
              end %end if 4

          end %end for loop 3
      else 
           fprintf('Temperature not within Range, Try again.');
      end %end if 2
  else
      fprintf('Invalid Data. Rerun program');
  end %end if 1

plot(T,mu,'-o');
grid on
legend('T','mu');
xlabel('Temperature, T/K');
ylabel('Viscosity (*10^-5 kg/ms');
title('Viscosity versus Temperature');

Answer 1

[Walter Roberson]

You can have at most one legend entry for each plot object. You are only plotting one line, so you can have only one legend entry.

You should not be trying to legend() each variable: that is what xlabel() and ylabel() are for.

[Walter Roberson]

If you want to point out a particular location on the plot, you should consider using annotation() or text(). legend() is mostly for the case that you have multiple graphics objects in a plot (such as multiple lines) and you want to give at key about which line has which meaning.

[NoDrivel]

Cheers. Nice day.

[Giuseppe Degan Di Dieco]

Dear Walter,

thanks for your tip on how the 'legend' function works.

It really helped me.

Best.