Improvements in 'FrequencyResponseResult'

[gutilacerda]

It would be interesting to change the calculation method performed in the "FrequencyResponseResult" class; it is possible to optimize it and obtain accurate results more quickly.

The calculation performed in "transfer_matrix" can be done using the rotor matrices directly, as shown below. There's no need to perform the integrations currently employed, which take more time to generate results.

$$\begin{equation} \textbf{H} = -\omega^2\textbf{M} + j\omega(\textbf{C}+\omega\textbf{G}) + \textbf{K} \end{equation}$$

Considering cases where many simultaneous simulations are required, such as uncertainty propagation, for example, any faster result generation is important.

[ross-bott]

Hi there!
I have marked this issue as stale because it has not had activity for 45 days.
Consider the following options:

• If the issue refers to a large task, break it in smaller issues that can be solved in
  less than 45 days;
• Label the issue as wontfix or wontfix for now and close it.