| Title: | Longitudinal Drift-Diffusion Mixed Models (LDDMM) |
|---|---|
| Description: | Implementation of the drift-diffusion mixed model for category learning as described in Paulon et al. (2021) <doi:10.1080/01621459.2020.1801448>. |
| Authors: | Giorgio Paulon [aut, cre], Abhra Sarkar [aut, ctb] |
| Maintainer: | Giorgio Paulon <[email protected]> |
| License: | MIT + file LICENSE |
| Version: | 0.4.2 |
| Built: | 2024-12-13 06:37:49 UTC |
| Source: | CRAN |
Construct the J basis functions for the splines evaluated on a grid.
B_basis(xgrid, knots)B_basis(xgrid, knots)
xgrid |
grid where we want to evaluate the spline functions (vector of length n) |
knots |
vector of knots for the splines (vector of length K) |
n x (K+1) - matrix representing the value of each basis function evaluated on xgrid
Function to compute the Watanabe-Akaike information criterion (Gelman, Hwang, Vehtari, 2014), which estimates the expected out-of-sample-prediction error using a bias-corrected adjustment of within-sample error.
compute_WAIC(model_fit)compute_WAIC(model_fit)
model_fit |
results of a model fit from the lddmm function |
A scalar indicating the WAIC (smaller WAIC denotes better fit)
A toy dataset in the correct format for the LDDMM function call. This dataset has two possible response categories.
datadata
A data frame with 24,254 rows and 6 columns
subject: vector of size n containing the participant labels
block: vector of size n containing the training blocks (longitudinal units)
s: vector of size n containing the stimuli
d: vector of size n containing the decisions
r_time: vector of size n containing the response times (log transformed)
cens: vector of size n containing the censoring indicators (1 censored, 0 non censored)
Function to extract the posterior draws of the parameters of interest from a lddmm fit object.
extract_post_draws(data, fit, par = c("drift", "boundary"))extract_post_draws(data, fit, par = c("drift", "boundary"))
data |
dataframe with the following columns:
|
fit |
fit from the lddmm function |
par |
parameter to output ('drift', or 'boundary') |
Matrix with the following columns:
subject: participant labels
block: training blocks
draw: iteration of the MCMC estimates
par_s_d, ...: posterior draws for the requested parameters
Function to extract the posterior means of the parameters of interest from a lddmm fit object.
extract_post_mean(data, fit, par = c("drift", "boundary"))extract_post_mean(data, fit, par = c("drift", "boundary"))
data |
dataframe with the following columns:
|
fit |
fit from the lddmm function |
par |
parameter to output ('drift', or 'boundary') |
Matrix with the following columns:
subject: participant labels
block: training blocks
par_s_d, ...: posterior means for the requested parameters
Computes the Hamming Ball centered at x with radius r.
H_ball(x, S, r)H_ball(x, S, r)
x |
center of the Hamming Ball |
S |
number of states |
r |
radius of the Hamming Ball |
Hamming Ball
Main function for the Gibbs sampler for the drift-diffusion model. Note that
priors are noninformative and calibrated so that, for the most stable
performance, the response times (variable r_time in the data dataframe)
should lie between 0 and 10.
LDDMM( data, hypers, cluster = TRUE, boundaries = "flexible", Niter = 5000, burnin = 2000, thin = 5 )LDDMM( data, hypers, cluster = TRUE, boundaries = "flexible", Niter = 5000, burnin = 2000, thin = 5 )
data |
dataframe with the following columns:
|
hypers |
hyperparameters of the MCMC: list containing "s_sigma_mu" and "s_sigma_b", which are the smoothness parameters for drifts and boundaries, respectively) |
cluster |
should clustering be used? (default = TRUE) |
boundaries |
whether to fit the unrestricted model (flexible), assume constant boundaries over time (constant) or fix the boundaries to the same level across predictors (fixed) |
Niter |
total number of iterations |
burnin |
burnin of the chain |
thin |
thinning factor |
List with the following MCMC posterior samples:
post_mean_delta: posterior samples for the population offset parameters
post_mean_mu: posterior samples for the population drift parameters
post_mean_b: posterior samples for the population boundary parameters
post_ind_delta: posterior samples for the individual offset parameters
post_ind_mu: posterior samples for the individual drift parameters
post_ind_b: posterior samples for the individual boundary parameters
sigma2_mu_us: posterior samples for the random effects drift smoothness parameters
sigma2_mu_ua: posterior samples for the random effects drift variance parameters
sigma2_b_us: posterior samples for the random effects boundary smoothness parameters
sigma2_b_ua: posterior samples for the random effects boundary variance parameters
sigma2_1_mu: posterior samples for the drift smoothness parameters
sigma2_1_b: posterior samples for the boundary smoothness parameters
pred_ans: predicted population-level categories
pred_time: predicted population-level response times
pred_ans_ind: predicted individual-level categories
pred_time_ind: predicted individual-level response times
Compute the log-likelihood for the drift-diffusion model, including the censored data contribution.
log_likelihood(tau, mu, b, delta, cens, D, log)log_likelihood(tau, mu, b, delta, cens, D, log)
tau |
vector of size n containing the response times |
mu |
matrix of size (n x d1) containing the drift parameters corresponding to the n response times for each possible d1 decision |
b |
matrix of size (n x d1) containing the boundary parameters corresponding to the n response times for each possible d1 decision |
delta |
vector of size n containing the offset parameters corresponding to the n response times |
cens |
vector of size n containing censoring indicators (1 censored, 0 not censored) corresponding to the n response times |
D |
(n x 2) matrix whose first column has the n input stimuli, and whose second column has the n decision categories |
log |
should the results be returned on the log scale? |
Compute the log-likelihood for the drift-diffusion model, including the censored data contribution, for a single observation.
log_likelihood_ind(tau, mu, b, delta, cens, D)log_likelihood_ind(tau, mu, b, delta, cens, D)
tau |
vector of size n containing the response times |
mu |
matrix of size (n x d1) containing the drift parameters corresponding to the n response times for each possible d1 decision |
b |
matrix of size (n x d1) containing the boundary parameters corresponding to the n response times for each possible d1 decision |
delta |
vector of size n containing the offset parameters corresponding to the n response times |
cens |
vector of size n containing censoring indicators (1 censored, 0 not censored) corresponding to the n response times |
D |
(n x 2) matrix whose first column has the n input stimuli, and whose second column has the n decision categories |
Construct the covariance matrix P of the smoothness inducing prior for the spline coefficients
P_smooth1(K)P_smooth1(K)
K |
Number of spline knots |
Covariance of the smoothness inducing prior (penalizing first differences in the spline coefficients)
Plot the accuracy of the raw data.
plot_accuracy(data)plot_accuracy(data)
data |
dataframe with the following columns:
|
Individual and population level raw accuracies
Function to plot the posterior mean and credible intervals of the parameters of interest from a lddmm fit object.
plot_post_pars(data, fit, par = c("drift", "boundary"))plot_post_pars(data, fit, par = c("drift", "boundary"))
data |
dataframe with the following columns:
|
fit |
fit from the lddmm function |
par |
parameter to output ('drift', or 'boundary') |
Posterior mean and 95% CI
Plot the mean response times of the raw data.
plot_RT(data)plot_RT(data)
data |
dataframe with the following columns:
|
Population level raw response times