R: Estimate the noise standard deviation

getsdofsb-methods {dti}

R Documentation

Estimate the noise standard deviation

Description

Estimate the noise standard deviation. Uses an assumption that the standard deviation is a linear function of the expected mean for image intensities. qA0 and qA1 define quantiles of observed image intensities that define the range of values where this assumption is made.

Usage

  ## S4 method for signature 'dtiData'
getsdofsb(object,qA0=.1,qA1=.98,nsb=NULL,level=NULL)

Arguments

`object`	Object of class `"dtiData"`
`qA0`	level for lower quantile of image intensities
`qA1`	level for upper quantile of image intensities
`nsb`	number of diffusion weighted image to use
`level`	level for mask

Value

An object of class "dtiData" with results in slot sdcoef in components 5: intercept parameter, 6: slope parameter for linear model, 7: lower bound (depending on qA0) and 8: upper bound (depending on qA1).

Methods

signature(object) = "ANY": Returns a warning.
signature(object) = "dtiData": Returns a dtiData object with estimated standard deviation parameters in slot sdcoef.

Author(s)

Karsten Tabelow tabelow@wias-berlin.de
J\"org Polzehl polzehl@wias-berlin.de