Estimates the global noise standard deviation from temporal differences,
assuming Rician magnitude noise that is approximately Gaussian at moderate SNR.
Usage
estimate_sigma_rician(vec, mask = NULL)
Arguments
- vec
4D fMRI data as a numeric array or `neuroim2::NeuroVec`.
- mask
Optional 3D logical/0-1 mask (array or `NeuroVol`). If `NULL`,
all voxels are used.
Value
A single numeric value: estimated noise sigma.
Examples
set.seed(1)
x <- array(100 + rnorm(10*10*10*5, sd=2), c(10,10,10,5))
estimate_sigma_rician(x)
#> [1] 1.508273