The task is about resonant circuits. $I(t)$ is the searched function and describes the chronological sequence of the amperage. In case of $ D:= \frac{1}{LC} -\frac{R^2}{4L^2} > 0$ you can describe $I(t) = Re \left( \frac{U_0}{L(-w^2 + \frac{R}{L} i w+ \frac{1}{LC})} \exp (iwt) \right) + \exp(- \frac{R}{2L}t)(\alpha \cos(\sqrt{D} t) +\beta sin(\sqrt{D}t))$.
I got the values for $ C,L,t, R,U_0, \alpha, \beta$ and a vector of values for $w$.
vt needs to be a vector of 200 equidistant values of the times $t$. $w$ is a vector with 50 values. My code:
>> D=(1/L*C)-((R^.2)/(4*L^.2)); >> sD= sqrt(D); >> vt=linspace(tmin,tmax,200); >> vw=omega; >> [vw,vt]=meshgrid(vw,vt); >> I= real((U0.*exp(i.*vw.*vt))./(L*(-vw.^2+ (R/L).*i.*vw + (1/L.*C))))+exp((-R.*vt)/(2.*L).*(alpha.*cos( sD.*vt)+ beta.*sin( sD.*vt))); >> surf(vw,vt,I) >>
Now, i am not sure if is really visualizing the sequence of the amperage right? It just doesnt look right to me, especially if i try other given values for $ C,L,t, R,U_0, \alpha, \beta, w $ I get a surf like :
In the equation just before the error, I think you want to type real rather than Re. Matlab thinks you have a variable called Re and that you want the umpty-umpth index, which is a complex number. Similarly, with $I(vt)$. As said by @FabioSomenzi, just use $I$. Another thing that you doing wrong is using trying to solve this for both frequency and time at the same time. I think something is wrong with your equation, You say that $I$ is a function of $t$, but the equation says it's a function of $\omega$ and $t$.