Newmark's is a method to solve higher-order differential equations without passing through the equivalent first-order system. It generalizes the so-called ‘leap-frog’ method. Here it is restricted to second-order equations.
function in the differential equation y'' = f(x, y, y');
start and end points of the interval.
starting values as row or column vector;
number of steps.
two non-negative real numbers.
Additional parameters to be passed to the function.
Solves second order differential equations using the Newmark method
on an equispaced grid of
f must return a vector, whose elements hold the evaluation
f(t,y), of the same dimension as
y0. Each row in the
solution array Y corresponds to a time returned in
The method is ‘implicit’ unless
zeta=theta=0, second order if
theta=1/2 and first order accurate if
theta>=1/2 ensures stability.
The condition set
theta=1/2; zeta=1/4 (the defaults) is a popular
approach that is unconditionally stable, but introduces oscillatory
spurious solutions on long time intervals.
(For these simulations it is preferable to use
No attempt is made to catch any errors in the root finding functions.
List with components
t for grid (or ‘time’) points between
y an n-by-2 matrix with solution variables in
columns, i.e. each row contains one time stamp.
This is for demonstration purposes only; for real problems or applications
Quarteroni, A., R. Sacco, and F. Saleri (2007). Numerical Mathematics. Second Edition, Springer-Verlag, Berlin Heidelberg.
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# Mathematical pendulum m l y'' + m g sin(y) = 0 pendel <- function(t, y) -sin(y) sol <- newmark(pendel, 0, 4*pi, c(pi/4, 0)) ## Not run: plot(sol$t, sol$y[, 1], type="l", col="blue", xlab="Time", ylab="Elongation/Speed", main="Mathematical Pendulum") lines(sol$t, sol$y[, 2], col="darkgreen") grid() ## End(Not run)
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