trialwise

Generate one regressor per trial (plus an optional grand-mean column) by delegating everything to hrf().

Usage

trialwise(
  basis = "spmg1",
  lag = 0,
  nbasis = 1,
  add_sum = FALSE,
  label = "trial"
)

Arguments

basis, lag, nbasis

Passed straight to hrf().

add_sum

If TRUE, append a column that is the average of all trialwise columns (useful as a conventional main effect).

label

Term label / prefix for the generated columns.

Value

An hrfspec term to be used on the RHS of an event-model formula.

Details

Use it only on the RHS of an event-model formula:

onset ~ trialwise(basis = "spmg1", add_sum = TRUE)

Examples

# Create example trial data for beta-series analysis
trial_data <- data.frame(
  onset = c(2, 8, 14, 20, 26),
  run = c(1, 1, 1, 1, 1)
)

# Create sampling frame (30 TRs, TR=2s)
sframe <- fmrihrf::sampling_frame(blocklens = 30, TR = 2)

# Basic trialwise model - creates one regressor per trial
emod_trials <- event_model(onset ~ trialwise(),
                          data = trial_data,
                          block = ~run,
                          sampling_frame = sframe)
print(emod_trials)
#> 
#> ── fMRI Event Model ────────────────────────────────────────────────────────────
#> Number of Terms: 1
#> Number of Events: 5
#> Number of Blocks: 1
#> Total Scans: 30
#> Design Matrix Dimensions: 30 x 5
#> 
#> ── Terms ──
#> 
#> • trial (<event_term>)
#> 
#> ── Design Matrix Preview ──
#> 
#>           trial_.trial_factor.length.onsets...1
#>    Scan 1   0.000                              
#>    Scan 2   0.048                              
#>    Scan 3   1.073                              
#>           trial_.trial_factor.length.onsets...2
#>    Scan 1   0.000                              
#>    Scan 2   0.000                              
#>    Scan 3   0.000                              
#>           trial_.trial_factor.length.onsets...3
#>    Scan 1   0.000                              
#>    Scan 2   0.000                              
#>    Scan 3   0.000                              
#>           trial_.trial_factor.length.onsets...4
#>    Scan 1   0.000                              
#>    Scan 2   0.000                              
#>    Scan 3   0.000                              
#> ...

# Trialwise with different basis and grand mean
emod_trials_mean <- event_model(onset ~ trialwise(basis = "spmg2", add_sum = TRUE),
                               data = trial_data,
                               block = ~run,
                               sampling_frame = sframe)
print(emod_trials_mean)
#> 
#> ── fMRI Event Model ────────────────────────────────────────────────────────────
#> Number of Terms: 1
#> Number of Events: 5
#> Number of Blocks: 1
#> Total Scans: 30
#> Design Matrix Dimensions: 30 x 11
#> 
#> ── Terms ──
#> 
#> • trial (<event_term>)
#> 
#> ── Design Matrix Preview ──
#> 
#>           trial_.trial_factor.length.onsets...1_b01
#>    Scan 1   0.000                                  
#>    Scan 2   0.048                                  
#>    Scan 3   1.073                                  
#>           trial_.trial_factor.length.onsets...2_b01
#>    Scan 1   0.000                                  
#>    Scan 2   0.162                                  
#>    Scan 3   0.654                                  
#>           trial_.trial_factor.length.onsets...3_b01
#>    Scan 1   0.000                                  
#>    Scan 2   0.000                                  
#>    Scan 3   0.000                                  
#>           trial_.trial_factor.length.onsets...4_b01
#>    Scan 1   0.000                                  
#>    Scan 2   0.000                                  
#>    Scan 3   0.000                                  
#> ...