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Simulate fMRI Noise

Source: R/simulate.R
simulate_noise_vector.Rd

This function simulates realistic fMRI noise by combining:

  • Temporal autocorrelation using an ARMA model

  • Low-frequency drift

  • Physiological noise (cardiac and respiratory)

Usage

simulate_noise_vector(
  n,
  TR = 1.5,
  ar = c(0.3),
  ma = c(0.5),
  sd = 1,
  drift_freq = 1/128,
  drift_amplitude = 2,
  physio = TRUE,
  seed = NULL
)

Arguments

n

The number of time points in the fMRI time series

TR

The repetition time in seconds (default is 1.5)

ar

A numeric vector containing autoregressive (AR) coefficients (default is c(0.3))

ma

A numeric vector containing moving average (MA) coefficients (default is c(0.5))

sd

The standard deviation of the white noise component (default is 1)

drift_freq

Frequency of the low-frequency drift in Hz (default is 1/128)

drift_amplitude

Amplitude of the low-frequency drift (default is 2)

physio

Logical; whether to add simulated physiological noise (default is TRUE)

seed

An optional seed for reproducibility (default is NULL)

Value

A numeric vector containing the simulated fMRI noise

Examples

# Simulate noise for a 5-minute scan with TR=2s
n_timepoints <- 150  # 5 minutes * 60 seconds / 2s TR
noise <- simulate_noise_vector(n_timepoints, TR = 2)
plot(noise, type = "l", xlab = "Time Point", ylab = "Signal")