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.

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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