fmri.detrend function

Detrend fMRI time series

Detrend fMRI dataset with a polynomial of given degree

fmri.detrend(data, degree = 1, nuisance=NULL, accoef = 0)

Arguments

• data: fMRI dataset of class ''fmridata''
• degree: Degree of the polynomial used to detrend the data. defaults to 1 (linear trends).
• nuisance: Matrix of additional nuisance parameters to regress against.
• accoef: Coefficient of AR(1) model used for prewhitening. default 0.

Details

The function can be used to detrend the time series of an fMRI dataset data (of class ''fmridata'' using polynomials. If the argument degree is larger than 0 (default: 1) the polynomial trends up to the given degree are removed from the data. If the argument accoef is larger than 0 (default: 0) prewhitening using an AR(1) model is performed.

Returns

Detrended data object of class ''fmridata''.

References

Polzehl, J. and Tabelow, K. (2007). fmri: A Package for Analyzing fmri Data, R News, 7:13-17.

Author(s)

Joerg Polzehl polzehl@wias-berlin.de

See Also

fmri.lm

Examples

# Example 1
  data <- list(ttt=writeBin(rnorm(32*32*32*107),raw(),4),
               mask=array(1,c(32,32,32)),dim=c(32,32,32,107))
  class(data) <- "fmridata"
  data <- fmri.detrend(data,2)