# how to get rid of imaginary numbers, after a root.

41 visualizaciones (últimos 30 días)
oskar el 25 de Oct. de 2013
Comentada: Kumaresh Kumaresh el 14 de Jun. de 2022
hi, i´m a beginner in matlab and i have been making a tracejtory with a basketball. my problem now is with the time.
This is a part of my script. My speed and angle are two vectors, because of the vectors sometimes the roots will be an imaginary number and (at=atand....) will get error. How do I do if i only want real numbers to go into at=atand....
time = roots([-g./2, v0y, y0-H]);
time = max(time);
at=atand((h0*cos(V))/((h0*sin(V))-(g*tid)));
##### 0 comentariosMostrar -2 comentarios más antiguosOcultar -2 comentarios más antiguos

Iniciar sesión para comentar.

Muruganandham Subramanian el 25 de Oct. de 2013
time = roots([-g./2, v0y, y0-H]);
time = max(time);
time=real(time);
at=atand((h0*cos(V))/((h0*sin(V))-(g*tid)))
##### 2 comentariosMostrar NingunoOcultar Ninguno
oskar el 25 de Oct. de 2013
thanks that is what i needed=)
Kumaresh Kumaresh el 14 de Jun. de 2022
Thanks ^^ Thas helps

Iniciar sesión para comentar.

### Más respuestas (2)

Simon el 25 de Oct. de 2013
Hi!
What do you expect, physically? Your trajectory is a parabola with negative prefactor in front of t^2. So, the apex is the highest point of your curve. If it is negative you won't find real roots of the polynom. Pyhsically this means you throw your ball from below the earth's surface and it is falling downwards ... ;-)
##### 0 comentariosMostrar -2 comentarios más antiguosOcultar -2 comentarios más antiguos

Iniciar sesión para comentar.

oskar el 25 de Oct. de 2013
I know, thats why i have two vectors wich will eventually get it into the baskethoop, but when the all the numbers "time" is going into the at=atand... i don't want the imaginary numbers to go into at=atand...
##### 1 comentarioMostrar -1 comentarios más antiguosOcultar -1 comentarios más antiguos
Simon el 25 de Oct. de 2013
If you just want to skip the atand command for imaginary time you may surround it with
if isreal(time)
atand ...
end

Iniciar sesión para comentar.

### Categorías

Más información sobre Tracking and Motion Estimation en Help Center y File Exchange.

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by