hbgd: Healthy birth, growth & development

Add a column to a data frame containing trajectory / velocity plots

add_trajectory_plot(dat, z = FALSE, center = FALSE, y_var = "htcm",
  x_range = NULL, nadir = FALSE, recovery = NULL, x_units = "days",
  width = 500, height = 520)

add_velocity_plot(dat, z = FALSE, center = FALSE, x_range = NULL,
  nadir = FALSE, recovery = NULL, x_units = "days", width = 500,
  height = 520)

`dat`	a data frame nested by subject and containing fits from `fit_all_trajectories`
`z`	should the trajectory fit be plotted on the z-scale?
`center`	should the trajectory be centered around the median WHO standard?
`y_var`	name of y variable to model (usually an anthropometric measure or z-score scaled anthropometric measure)
`x_range`	a vector specifying the range (min, max) that the superposed WHO growth standard should span on the x-axis
`nadir`	should a guide be added to the plot showing the location of the nadir? (only valid when z = TRUE)
`recovery`	age in days at which to plot recovery from nadir (only valid when z = TRUE) - if NULL (default), will not be plotted
`x_units`	units of age x-axis ("days", "months", or "years")
`width`	width of the plot
`height`	height of the plot

## Not run: 
cppsubj  <- by_subject(cpp)
cppfit   <- get_fit(cpp, method = "rlm")
cpptr    <- fit_all_trajectories(cppsubj, cppfit)
cppplot  <- trscope_trajectories(cpptr)
cppzplot <- trscope_trajectories(cpptr, z = TRUE, nadir = TRUE, x_units = "months")

## End(Not run)