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.