I have a hundred time series, all sampled at the same time interval. I did an FFT of all of these time series and arranged them row by row in a matrix ($\mathbf{X}$). I have a target variable ($\mathbf{y}$) for each time series. I then solve the multiple linear regression equation:
$$ \mathbf{y} = \mathbf{X}\,\boldsymbol{\beta} + \boldsymbol{\varepsilon} $$
I want to plot the $\boldsymbol{\beta}$ back on the FFT spectrum to see which FFT spectrum is the most useful in predicting $\mathbf{y}$.
Does this make any sense?