 RungeKutta - Maple Help

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Student[NumericalAnalysis]

 RungeKutta
 numerically approximate the solution to a first order initial-value problem with the Runge-Kutta Method Calling Sequence RungeKutta(ODE, IC, t=b, opts) RungeKutta(ODE, IC, b, opts) Parameters

 ODE - equation; first order ordinary differential equation of the form $\frac{ⅆ}{ⅆt}\phantom{\rule[-0.0ex]{0.4em}{0.0ex}}y\left(t\right)=f\left(t,y\right)$ IC - equation; initial condition of the form y(a)=c, where a is the left endpoint of the initial-value problem t - name; the independent variable b - algebraic; the point for which to solve; the right endpoint of this initial-value problem opts - (optional) equations of the form keyword=value, where keyword is one of numsteps, output, comparewith, digits, plotoptions, or submethod; options for numerically solving the initial-value problem Options

 • comparewith = [list]
 A list of method-submethod pairs; the method specified in the method option will be compared graphically with these methods. This option may only be used if output is set to either plot or information.
 It must be of the form
 comparewith = [[method_1, submethod_1], [method_2, submethod_2]]
 If either method lacks applicable submethods, the corresponding submethod_n entry should be omitted.
 Lists of all supported methods and their submethods are found in the InitialValueProblem help page, under the descriptions for the method and submethod options, respectively.
 • digits = posint
 The number of digits to which the returned values will be rounded (using evalf). The default value is 4.
 • numsteps = posint
 The number of steps used for the chosen numerical method. This option determines the static step size for each iteration in the algorithm. The default value is 5.
 Controls what information is returned by this procedure. The default value is solution:
 – output = solution returns the computed value of $y\left(t\right)$ at $t$ = b;
 – output = Error returns the absolute error of $y\left(t\right)$ at $t$ = b;
 – output = plot returns a plot of the approximate (Runge-Kutta) solution and the solution from one of Maple's best numeric DE solvers; and
 – output = information returns an array of the values of $t$, Maple's numeric solution, the approximations of $y\left(t\right)$ as computed using this method and the absolute error between these at each iteration.
 • plotoptions = list
 The plot options. This option is used only when output = plot is specified.
 • submethod = midpoint, rk3, rk4, rkf, heun, or meuler
 The Runge-Kutta submethod used to solve this initial-value problem.
 – midpoint = Midpoint Method
 – rk3 = Order Three Method
 – rk4 = Order Four Method
 – rkf = Runge-Kutta-Fehlberg Method
 – heun = Heun Method
 – meuler = Modified Euler Method
 By default the Runge-Kutta Midpoint Method is used. Description

 • Given an initial-value problem consisting of an ordinary differential equation ODE, a range a <= t <= b, and an initial condition y(a) = c, the RungeKutta command computes an approximate value of y(b) using the Runge-Kutta methods.
 • If the second calling sequence is used, the independent variable t will be inferred from ODE.
 • The endpoints a and b must be expressions that can be evaluated to floating-point numbers. The initial condition IC must be of the form y(a)=c, where c can be evaluated to a floating-point number.
 • The RungeKutta command is a shortcut for calling the InitialValueProblem command with the method = rungekutta option. Notes

 • To approximate the solution to an initial-value problem using a method other than the Runge-Kutta Method, see InitialValueProblem. Examples

 > $\mathrm{with}\left(\mathrm{Student}\left[\mathrm{NumericalAnalysis}\right]\right):$
 > $\mathrm{RungeKutta}\left(\mathrm{diff}\left(y\left(t\right),t\right)=\mathrm{cos}\left(t\right),y\left(0\right)=0.5,t=3,\mathrm{submethod}=\mathrm{rk4}\right)$
 ${0.6411}$ (1)
 > $\mathrm{RungeKutta}\left(\mathrm{diff}\left(y\left(t\right),t\right)=\mathrm{cos}\left(t\right),y\left(0\right)=0.5,t=3,\mathrm{submethod}=\mathrm{rk4},\mathrm{output}=\mathrm{plot}\right)$ 