This function estimates the parameters of a piecewise linear model for the dependence between error standard deviation and mean.
# S4 method for dtiData
sdpar(object,level=NULL,sdmethod="none",interactive=TRUE,threshfactor=1)The function returns an object of class dtiData.
An object of class dtiData
Suggested value for slot level. As a default the value in object@level is used. The value determines the lower endpoint of the linear section in the model for error standard deviation as a function of the mean.
Method for estimating voxelwise standard deviations if replicates of zero weighted images are available, can be set to "sd" or "mad". "none" specifies that no variance model is fitted
If TRUE a density of values in zero weighted images is plotted together with
the specification of the lower endpoint of the interval of linearity. A good choice of this point should correspond, if present, to the minimum between the first two modes of the density estimate. The value can be changed or accepted. If changed a new value for slot lambda is set.
Factor for threshold-value selected if function is run in interactive mode. May be used to correct results if automatic threshold selection fails.
Returns a warning
Estimate parameters of a model for the dependence between error standard deviation and mean.
Karsten Tabelow tabelow@wias-berlin.de
J\"org Polzehl polzehl@wias-berlin.de
dtiData,
readDWIdata,
dti.smooth,
dtiTensor,