R

log likelihood in r

# Calculate the log-likelihood for each term
log_likelihoods <- log(y_pred) * y_actual + log(1 - y_pred) * (1 - y_actual)

# Calculate minus the sum of the log-likelihoods for each term
-sum(log_likelihoods)

#function
calc_neg_log_likelihood <- function(coeffs) {
  intercept <- coeffs[1]
  slope <- coeffs[2]
  y_pred <- plogis(intercept + slope * x_actual)
  log_likelihoods <- log(y_pred) * y_actual + log(1 - y_pred) * (1 - y_actual)
  -sum(log_likelihoods)
}