Covariance computation#

`Covariance`(data, names, bads, projs, nfree)	Noise covariance matrix.
`compute_covariance`(epochs[, ...])	Estimate noise covariance matrix from epochs.
`compute_raw_covariance`(raw[, tmin, tmax, ...])	Estimate noise covariance matrix from a continuous segment of raw data.
`cov.compute_whitener`(noise_cov[, info, ...])	Compute whitening matrix.
`cov.prepare_noise_cov`(noise_cov, info[, ...])	Prepare noise covariance matrix.
`cov.regularize`(cov, info[, mag, grad, eeg, ...])	Regularize noise covariance matrix.
`compute_rank`(inst[, rank, scalings, info, ...])	Compute the rank of data or noise covariance.
`make_ad_hoc_cov`(info[, std, verbose])	Create an ad hoc noise covariance.
`read_cov`(fname[, verbose])	Read a noise covariance from a FIF file.
`write_cov`(fname, cov, *[, overwrite, verbose])	Write a noise covariance matrix.