[quote author=Fu-Kwun Hwang link=topic=907.msg3408#msg3408 date=1233239358]
You are differential it in time, so it should not matter if your points are spread out in space.
I do not understand why you said it is not working. May be you have another problem.

And becareful: It is not correct to write something like sin(x-t)
x and t is not the same dimension. You can not substract time from space

You can write sin(k*x-w*t). But sin(x-t) is meanless.
[/quote]

LOL agreed, sin(k*x-w*t), i was assuming k =1 and w =1 for quick typing :)

i now get strange simulation, think i debug tomorrow

found one bug!!
dudt = (u2-u)/ddt; // () is so important :)

let me give it some time to crack it before i ask u again :)

think i need
du/dx =  k*cos ( k*x - w*t) from a string u = sin ( k*x - w*t) instead of du/dt