1×0 empty double row vector with command find

Hi everyone, I am trying to find the intersections points in the figure, but when I use the command find I just get this error:

1×0 empty double row vector

This is my code

Vo1=50;        
Vo2=80;        
g=-9.81;      
t_v=0:0.1:20;   

h_1=Vo1*t_v+(g*t_v.^2)/2;           
h_2=Vo2*(t_v-2)+(g*(t_v-2).^2/2);   

figure
plot(t_v,h_1,'m',t_v,h_2,'b') ;            
grid on;
title('Trayectorias');
xlabel('Tiempo');
ylabel('Altura');
axis([0 10 0 340]);
legend('Velocidad 50','Velocidad 80','fontsize',14);
find(h_1==h_2)

thanks

Answer 1

[Jan]

Why do you call this an "error"? The vectors h_1 and h_2 do not have an equal element at the same location. h_1==h_2 is an elementwise comparison, which relplies a vactor. Do you want to compare all elements with eachother? Then you need:

find(h_1 == h_2.')

Even then it is not expected, that you find identical elements due to the rounding errors. You need a tolerance:

find(abs(h_1 - h_2.') < 10 * eps(max(h_1, h_2)))