HRF Constructor Function — HRF • fmrihrf

The `HRF` function creates an object representing a hemodynamic response function (HRF). It is a class constructor for HRFs.

Usage

HRF(fun, name, nbasis = 1, span = 24, param_names = NULL)

Arguments

fun: A function representing the hemodynamic response, mapping from time to BOLD response.
name: A string specifying the name of the function.
nbasis: An integer representing the number of basis functions, e.g., the columnar dimension of the HRF. Default is 1.
span: A numeric value representing the span in seconds of the HRF. Default is 24.
param_names: A character vector containing the names of the parameters for the HRF function.

Value

An HRF object with the specified properties.

Details

The package provides several pre-defined HRF types that can be used in modeling fMRI responses:

**Canonical HRFs:** * `"spmg1"` or `HRF_SPMG1`: SPM's canonical HRF (single basis function) * `"spmg2"` or `HRF_SPMG2`: SPM canonical + temporal derivative (2 basis functions) * `"spmg3"` or `HRF_SPMG3`: SPM canonical + temporal and dispersion derivatives (3 basis functions) * `"gaussian"` or `HRF_GAUSSIAN`: Gaussian-shaped HRF with peak around 5-6s * `"gamma"` or `HRF_GAMMA`: Gamma function-based HRF with longer tail

**Flexible basis sets:** * `"bspline"` or `"bs"` or `HRF_BSPLINE`: B-spline basis for flexible HRF modeling * `"tent"`: Tent (triangular) basis functions for flexible HRF modeling * `"daguerre"` or `HRF_DAGUERRE`: Daguerre basis functions

To see a complete list of available HRF types with details, use the `list_available_hrfs()` function.

Examples

hrf <- HRF(hrf_gamma, "gamma", nbasis=1, param_names=c("shape", "rate"))
resp <- evaluate(hrf, seq(0, 24, by=1))

# List all available HRF types
list_available_hrfs(details = TRUE)
#>        name      type nbasis_default is_alias                description
#> 1     spmg1    object              1    FALSE        spmg1 HRF (object) 
#> 2     spmg2    object              2    FALSE        spmg2 HRF (object) 
#> 3     spmg3    object              3    FALSE        spmg3 HRF (object) 
#> 4     gamma    object              1    FALSE        gamma HRF (object) 
#> 5  gaussian    object              1    FALSE     gaussian HRF (object) 
#> 6   bspline generator              5    FALSE   bspline HRF (generator) 
#> 7      tent generator              5    FALSE      tent HRF (generator) 
#> 8   fourier generator              5    FALSE   fourier HRF (generator) 
#> 9  daguerre generator              3    FALSE  daguerre HRF (generator) 
#> 10      fir generator             12    FALSE       fir HRF (generator) 
#> 11      lwu generator       variable    FALSE       lwu HRF (generator) 
#> 12      gam    object              1    FALSE          gam HRF (object) 
#> 13       bs generator              5     TRUE bs HRF (generator) (alias)