FD {fMRIscrub} | R Documentation |
Framewise Displacement
Description
Calculate Framewise Displacement (FD)
Usage
FD(
X,
trans_units = c("mm", "cm", "in"),
rot_units = c("deg", "rad", "mm", "cm", "in"),
brain_radius = NULL,
detrend = FALSE,
lag = 1,
cutoff = 0.3
)
Arguments
X |
An Alternatively, this can be the file path to an |
trans_units |
|
rot_units |
|
brain_radius |
If If |
detrend |
Detrend each RP with the DCT before computing FD?
Default: |
lag |
The difference of indices between which to calculate change in
position. Default: |
cutoff |
FD values higher than this will be flagged. Default: |
Details
The FD formula is taken from Power et. al. (2012):
where is the timepoint;
,
and
are the
translational realignment parameters (RPs);
,
and
are the rotational RPs;
and
(and similarly for the other RPs).
Value
A list with components
- measure
A length
vector of FD values in
trans_units
.- measure_info
"FD"
- outlier_cutoff
cutoff
- outlier_flag
A length-N logical vector, where
TRUE
indicates suspected outlier presence.
References
Power, J. D., Barnes, K. A., Snyder, A. Z., Schlaggar, B. L. & Petersen, S. E. Spurious but systematic correlations in functional connectivity MRI networks arise from subject motion. Neuroimage 59, 2142-2154 (2012).