Compute F-contrasts
Usage
Fcontrasts(x, ...)
# S3 method for class 'convolved_term'
Fcontrasts(x, ...)
# S3 method for class 'event_model'
Fcontrasts(x, ...)
# S3 method for class 'feature_term'
Fcontrasts(x, ...)Details
Row names of the contrast matrices can specify which levels of the term are tested. Any matching is done against the design matrix column names.
For terms with a multi-basis HRF (e.g. "spmg2", "spmg3", FIR), the
term-level contrast \(C\) (one row per condition) is expanded to
\(C \otimes I_{nb}\): the condition effect is
tested jointly in every basis function, so a term with \(k\) conditions
and \(nb\) basis functions yields a \((k \cdot nb) \times ((k-1) \cdot nb)\)
matrix for its main effect. Columns are named <contrast column>_b##.
Terms with no categorical variable (e.g. hrf(rt), covariates, feature
terms) contribute no F-contrasts; a model made only of such terms returns
an empty list. Calling Fcontrasts() directly on such an event_term
still signals an error.
Examples
des <- data.frame(
onset = c(0, 10, 20, 30),
run = 1,
cond = factor(c("A", "B", "A", "B"))
)
sframe <- fmrihrf::sampling_frame(blocklens = 40, TR = 1)
emod <- event_model(onset ~ hrf(cond), data = des, block = ~run, sampling_frame = sframe)
names(Fcontrasts(emod))
#> [1] "cond#cond"