variance: Variance
In be5tan/rlystop: Early stopping for statistical inverse problems

Computes the variance of the m-th filter estimator, a given diagonal design matrix lambda and noise level delta.

1	variance(m, lambda, delta, alpha = -1, filt = c("cutoff", "landw"))

`m`	Integer stopping index.
`lambda`	Vector of decreasing, strictly positive entries of the diagonal design matrix.
`delta`	Numeric noise level.
`alpha`	Numeric smoothing parameter. `alpha` = -1 gives the strong bias. `alpha` = 0 gives the weak bias.
`filt`	Character string designating the filter to be used. filt should be one of "cutoff" or "landw".