Returns a scale estimation as calculated by the (robust) Qn estimator.
Usage
qn(x, corrFact)
Arguments
x
a vector of data
corrFact
the finite sample bias correction factor. By default a value of ~ 2.219144 is used (assuming normality).
Details
The Qn estimator computes the first quartile of the pairwise absolute
differences of all data values.
Value
The estimated scale of the data.
Warning
Earlier implementations used a wrong correction factor for the final result. Thus qn estimations computed with package pcaPP version > 1.8-1 differ about 0.12% from earlier estimations (version <= 1.8-1).
Note
See the vignette "Compiling pcaPP for Matlab" which comes with this package to compile and use this function in Matlab.