Function impulse 

pub fn impulse(
    laplacian: &CsMat<f64>,
    vertex_index: usize,
    n_channels: usize,
) -> Result<Array2<f64>, GspError>

Builds a one-hot impulse matrix for n_timesteps columns.

Errors

Returns an error when the impulse index is out of bounds or n_timesteps == 0.