The line on the legend are not showing

When i try plotting a legend i end up with only the names of the curves. But when i change the type of line of my curves like if i put . or o, it is showing on my graph but not for a continuous line. i tried a few different way to put the legend, manually or just trusting matlab but it doesn't work.

Here's my code

a_1 = plot(X_1,Y_1, 'b-', 'DisplayName', "Onde incidente");
hold on ;
a_2 = plot(X_2, Y_2,'r-', 'DisplayName', "Onde transmise");
title("Signal experimental Mousse G");
legend show;
xlabel("temps (s)");
ylabel("amplitude");

Answer 1

[Walter Roberson]

What you describe sounds as if either X_1 or Y_1 are scalars. In such a case, requesting . or o will draw markers, but there would be no finite (x,y) pairs to draw lines between.

Lower probability is if X_1 or Y_1 happens to be such that it has infinite or nan entries between every finite entry.

x = 1:5;
y = [1 nan inf 4 nan];
subplot(2,1,1)
plot(x,y)
xlim([0 5]); ylim([0 5])

subplot(2,1,2)
plot(x,y,'o-')
xlim([0 5]); ylim([0 5])

The first plot does not show any lines because lines are only drawn if there are adjacent finite coordinates.