# Function that produces Half-life property for a single individual in a particular group, for a specific metabolite ```r calculate_half_life(f, Tmax, Cmax) ``` ## Arguments - `f`: function that returns the prediction of a metabolite concentration, for a single individual in a particular group - `Tmax`: Tmax property of a metabolite, for a single individual in a particular group - `Cmax`: Cmax property of a metabolite, for a single individual in a particular group ## Returns Half-life for this metabolite, in a particular group for a single individual ## Examples ```r require(gammaFuncModel) require(rootSolve) require(dplyr) require(nlme) modify.df <- data.frame( ID = rep(sprintf("%02d", 1:10), each = 9 * 3), Time = rep(rep(1:9, each = 3), 10), Diet = as.factor(rep(1:3, times = 9 * 10)), Age = rep(sample(20:70, 10, replace = TRUE), each = 9 * 3), BMI = round(rep(runif(10, 18.5, 35), each = 9 * 3), 1), Concentration = NA ) for (i in 1:10) { for (d in 1:3) { C0 <- runif(1, 10, 15) # initial concentration k <- runif(1, 0.1, 0.3) # decay rate constant modify.df$Concentration[modify.df$ID == sprintf("%02d", i) & modify.df$Diet == d] <- C0 * exp(-k * modify.df$Time[modify.df$ID == sprintf("%02d", i) & modify.df$Diet == d]) } } covariates <- c("ID", "Diet", "Age", "BMI") model <- gammaFunction( modify.df, covariates, time_grp_inter = FALSE, return_ml_model = FALSE, include_grp = TRUE )[[1]] test_data = modify.df %>% filter(Diet == 1 & ID == "03") %>% select(-c("Concentration", "ID", "Diet")) Tmax <- calculate_Tmax(data = test_data, model, grp_var = 1, ID = "03", grp_name = 'Diet', ref = 1) Cmax <- calculate_Cmax(data = test_data, model, grp_var = 1, ID = "03", grp_name = "Diet", Tmax) f_dat = modify.df %>% filter(Diet == 1 & ID == "03") %>% select(-Concentration) f <- generate_f_function( data = f_dat, model = model, grp_var = 1, grp_name = "Diet", ID = "03", ref = 1) half_life <- calculate_half_life(f, Tmax, Cmax) ``` ## References Wickham, H. (2022). dplyr: A Grammar of Data Manipulation. R package version 1.0.10. Available at: [https://CRAN.R-project.org/package=dplyr](https://CRAN.R-project.org/package=dplyr) Pinheiro, J. C., & Bates, D. M. (2022). nlme: Linear and Nonlinear Mixed Effects Models. R package version 3.1-153. Available at: [https://CRAN.R-project.org/package=nlme](https://CRAN.R-project.org/package=nlme)

calculate_half_life function