# getEnergy Get the calculated energy level ```r getEnergy(object, ...) ``` ## Arguments - `object`: a class object - `...`: additional parameters ## Examples ```r # KeplerEnergy.R # setClass("KeplerEnergy", slots = c( GM = "numeric", odeSolver = "Verlet", counter = "numeric" ), contains = c("ODE") ) setMethod("initialize", "KeplerEnergy", function(.Object, ...) { .Object@GM <- 4 * pi * pi # gravitation constant times combined mass .Object@state <- vector("numeric", 5) # x, vx, y, vy, t # .Object@odeSolver <- Verlet(ode = .Object) .Object@odeSolver <- Verlet(.Object) .Object@counter <- 0 return(.Object) }) setMethod("doStep", "KeplerEnergy", function(object, ...) { object@odeSolver <- step(object@odeSolver) object@state <- object@odeSolver@ode@state object }) setMethod("getTime", "KeplerEnergy", function(object, ...) { return(object@state[5]) }) setMethod("getEnergy", "KeplerEnergy", function(object, ...) { ke <- 0.5 * (object@state[2] * object@state[2] + object@state[4] * object@state[4]) pe <- -object@GM / sqrt(object@state[1] * object@state[1] + object@state[3] * object@state[3]) return(pe+ke) }) setMethod("init", "KeplerEnergy", function(object, initState, ...) { object@state <- initState object@odeSolver <- init(object@odeSolver, getStepSize(object@odeSolver)) object@counter <- 0 object }) setReplaceMethod("init", "KeplerEnergy", function(object, ..., value) { initState <- value object@state <- initState object@odeSolver <- init(object@odeSolver, getStepSize(object@odeSolver)) object@counter <- 0 object }) setMethod("getRate", "KeplerEnergy", function(object, state, ...) { # Computes the rate using the given state. r2 <- state[1] * state[1] + state[3] * state[3] # distance squared r3 <- r2 * sqrt(r2) # distance cubed object@rate[1] <- state[2] object@rate[2] <- (- object@GM * state[1]) / r3 object@rate[3] <- state[4] object@rate[4] <- (- object@GM * state[3]) / r3 object@rate[5] <- 1 # time derivative object@counter <- object@counter + 1 object@rate }) setMethod("getState", "KeplerEnergy", function(object, ...) { # Gets the state variables. return(object@state) }) # constructor KeplerEnergy <- function() { kepler <- new("KeplerEnergy") return(kepler) } ```

getEnergy-method function