demo/RigidBodyNXFApp.R

In rODE: Ordinary Differential Equation (ODE) Solvers Written in R Using S4 Classes

# +++++++++++++++++++++++++++++++++++++++++++++++ application: RigidBodyNXFApp.R
# example of a nonstiff system is the system of equations describing
# the motion of a rigid body without external forces.

importFromExamples("RigidBody.R")

# run the application
RigidBodyNXFApp <- function(verbose = FALSE) {
    # load the R class that sets up the solver for this application
    y1 <- 0   # initial y1 value
    y2 <- 1    # initial y2 value
    y3 <- 1    # initial y3 value
    dt        <- 0.01 # delta time for step

    body   <- RigidBodyNXF(y1, y2, y3)
    solver <- Euler(body)
    solver <- setStepSize(solver, dt)
    rowVector <- vector("list")
    i <- 1
    # stop loop when the body hits the ground
    while (getState(body)[4] <= 12) {
        rowVector[[i]] <- list(t  = getState(body)[4],
                               y1 = getState(body)[1],
                               y2 = getState(body)[2],
                               y3 = getState(body)[3])
        solver <- step(solver)
        body   <- getODE(solver)
        i <- i + 1
    }
    DT <- data.table::rbindlist(rowVector)
    return(DT)
}

# get the data table from the app
solution <- RigidBodyNXFApp()
plot(solution)