java - Calculating an object's position, velocity and other derivatives of motion efficiently -
ok, here's programming/physics puzzle in, let's java (although doesn't matter - consistency, use java).
i have array of doubles each element represents successive derivates of object's position. so:
d[0] // position d[1] // velocity d[2] // accelleration
etc ...
there @ least 1 , potentially number of elements (but in practice, not more 5). elements beyond end of array assumed zero.
we have double t
time.
so if d.length
3 specifically:
d[0] += d[1] * t + d[2] * t * t / 2 d[1] += d[2] * t
but how can write iterative solution (no recursion!) update of elements of array time t length of a?
votes should awarded efficiency , conciseness.
edit: laws of motion on physics pages of site, each term has form:
power(t,n) / factorial(n)
so next term of first equation d[3] * t*t*t / 6
if not familiar these equations, please don't ask me explain.
a test case:
final static double[] d = { 5.0, 4.0, 3.0, 2.0, 1.0 }; double t = 10.0
should give:
[945.0, 300.66666666666663, 73.0, 12.0, 1.0]
second element may vary due precision errors.
i think works.
int length = d.length; (int = 0; < length - 1; i++) { double temp = 0; (int j = length - 1; j > i; j--) temp = (temp + d[j]) * t / (j - i); d[i] += temp; }
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