1d:T732,# Generate probabilities of seropositivity by age based on a general Force-of-Infection (FoI) model. This function calculates the probabilities of seropositivity by age based on an abstract model of the serocatalytic system. ```r prob_seroprev_gen_by_age( construct_A_fun, calculate_seroprev_fun, initial_conditions, max_age, ... ) ``` ## Arguments - `construct_A_fun`: A function that constructs a matrix that defines the multiplier term in the linear ODE system. - `calculate_seroprev_fun`: A function which takes the state vector and returns the seropositive fraction. - `initial_conditions`: The initial state vector proportions for each birth cohort. - `max_age`: The maximum age to simulate seropositivity for. - `...`: Additional parameters for `construct_A_fun` ## Returns A dataframe with columns 'age' and 'seropositivity'. ## Examples ```r # define age- and time-specific multipliers foi_df_time <- data.frame( year = seq(1946, 2025, 1), foi = c(rep(0, 40), rep(1, 40)) ) foi_df_age <- data.frame( age = 1:80, foi = 2 * dlnorm(1:80, meanlog = 3.5, sdlog = 0.5) ) u <- foi_df_age$foi v <- foi_df_time$foi # function to construct A matrix for one piece construct_A <- function(t, tau, u, v) { u_bar <- u[t - tau] v_bar <- v[t] A <- diag(-1, ncol = 12, nrow = 12) A[row(A) == (col(A) + 1)] <- 1 A[1, 1] <- -u_bar * v_bar A[2, 1] <- u_bar * v_bar A[12, 12] <- 0 A } # determines the sum of seropositive compartments of those still alive calculate_seropositivity_fn <- function(Y) { sum(Y[2:11]) / (1 - Y[12]) } # initial conditions in 12D state vector initial_conditions <- rep(0, 12) initial_conditions[1] <- 1 # calculate probability seropositive_hiv <- prob_seroprev_gen_by_age( construct_A, calculate_seropositivity_fn, initial_conditions, max_age = 80, u, v ) ```1e:T49a,M7.49933 0.25C3.49635 0.25 0.25 3.49593 0.25 7.50024C0.25 10.703 2.32715 13.4206 5.2081 14.3797C5.57084 14.446 5.70302 14.2222 5.70302 14.0299C5.70302 13.8576 5.69679 13.4019 5.69323 12.797C

prob_seroprev_gen_by_age function