Obtain seperate legend for each contour line

Hello everyone

%% sin(t)-(1/(1.5*V));
figure
[t,V]=meshgrid(-5:0.33:5,-5:0.3:5);
slope=sin(t)-(V./1.5);
length=sqrt(1+slope.^2);

quiver(t,V,1./length,slope./length,0.79);
xlabel('t in s')
ylabel('V(t)')
box on
title('slope field equation (2)')
legend('slope field')
yticks([-5:5:5]);
xticks([-6:2:6]);
axis([-6 6 -5 5])
hold on
c=[-2:1:2];
[C,h]=contour('v6',t,V,slope,c);

Here is my code but it displays the legend as in figure 1. I want the legend to be like in figure 2.

The legend in fi1 is placed in data1. I don't want to do it like that. I want every line to have its own legend

UPDATE!!!!!!!!!!!!!!!!: found the solution here

https://de.mathworks.com/matlabcentral/answers/284500-contour-plot-legend-how-to-change-symbol-to-straight-line

Answer 1

[dpb]

There's no way to make legend use the contour lines directly; there are not any object handles to them; and the legend is global to the object as you observe.

Again, one has to revert to subterfuge --

...
hQ=quiver(t,V,1./length,slope./length,0.79);    % save handle
...
[C,hC]=contour('v6',t,V,slope,c);               % identify handle
i1=2:C(2,1)+1:size(C,2);                        % retrieve beginning of contour lines
clr={'r','o','m','g','c'};                      % define some colors -- not very distinct, could do better
hL=arrayfun(@(i,c) plot(C(1,i:i+60),C(2,i:i+60), ...
    ['-' c{:}],'DisplayName',num2str(C(1,i-1),'incline %d V/s')),i1,clr);   % draw the contour lines
hLg=legend([hQ hL]);                            % legend for only objects wanted

produced:

Would seem worthy of enhancement request to contour altho I have serious doubts would ever be addressed...they think you're supposed to label the contour lines themselves instead.

[Mehdi Jaiem]

Smart ! although it took me some time to understand it but the idea is good

I also found a dummy way to plot the legend .. hang on .. it's not that perfect idea but it did the job.

Simply ploted empty graphs and assigned a legend to them.

[t,V]=meshgrid(-5:0.35:5,-5:0.35:5);
slope=1-V-t;
length=sqrt(1+slope.^2);
hQ=quiver(t,V,1./length,slope./length,0.75);
xlabel('t in s')
ylabel('V(t)')
box on
title('slope field equation (1) ')
yticks([-5:5:5]);
xticks([-6:2:6]);
axis([-6 6 -5 5])
hold on;
c=[-2,-1,0,1,2];
[C,h]=contour(t,V,slope,c);
hm2 = plot(NaN);
hm1 = plot(NaN);
h0 = plot(NaN);
h1 = plot(NaN);
h2 = plot(NaN);
legend([hQ hm2 hm1 h0 h1 h2],'slope field','isocline -2 V/s', 'isocline -1 V/s','isocline 0 V/s','isocline 1 V/s','isocline 2 V/s');