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

## Description

New setState that should work with different methods "theta", "thetaDot": used in PendulumApp "x", "vx", "y", "vy": used in ProjectileApp

## Usage

 `1` ```setState(object, ...) ```

## Arguments

 `object` a class object `...` additional parameters

## Examples

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72``` ```# +++++++++++++++++++++++++++++++++++++++++++++++++ application: ProjectileApp.R # test Projectile with RK4 # originally uses Euler # suppressMessages(library(data.table)) importFromExamples("Projectile.R") # source the class ProjectileApp <- function(verbose = FALSE) { # initial values x <- 0; vx <- 10; y <- 0; vy <- 10 state <- c(x, vx, y, vy, 0) # state vector dt <- 0.01 projectile <- Projectile() projectile <- setState(projectile, x, vx, y, vy) projectile@odeSolver <- init(projectile@odeSolver, 0.123) # init(projectile) <- 0.123 projectile@odeSolver <- setStepSize(projectile@odeSolver, dt) rowV <- vector("list") i <- 1 while (getState(projectile)[3] >= 0) { rowV[[i]] <- list(t = getState(projectile)[5], x = getState(projectile)[1], vx = getState(projectile)[2], y = getState(projectile)[3], # vertical position vy = getState(projectile)[4]) projectile <- step(projectile) i <- i + 1 } DT <- data.table::rbindlist(rowV) return(DT) } solution <- ProjectileApp() plot(solution) # ++++++++++++++++++++++++++++++++++++++++++++++++++ example: PendulumApp.R # Simulation of a pendulum using the EulerRichardson ODE solver suppressPackageStartupMessages(library(ggplot2)) importFromExamples("Pendulum.R") # source the class PendulumApp <- function(verbose = FALSE) { # initial values theta <- 0.2 thetaDot <- 0 dt <- 0.1 pendulum <- Pendulum() # pendulum@state[3] <- 0 # set time to zero, t = 0 pendulum <- setState(pendulum, theta, thetaDot) pendulum <- setStepSize(pendulum, dt = dt) # using stepSize in RK4 pendulum@odeSolver <- setStepSize(pendulum@odeSolver, dt) # set new step size rowvec <- vector("list") i <- 1 while (getState(pendulum)[3] <= 40) { rowvec[[i]] <- list(t = getState(pendulum)[3], # time theta = getState(pendulum)[1], # angle thetadot = getState(pendulum)[2]) # derivative of angle pendulum <- step(pendulum) i <- i + 1 } DT <- data.table::rbindlist(rowvec) return(DT) } # show solution solution <- PendulumApp() plot(solution) ```

rODE documentation built on May 1, 2019, 10:17 p.m.