[Help-gsl] RK4 Help required

[cigdem ozkan]

Hi again,
I am posting a smaller version of my question rearding rk4 since I didnt get a 
reply and I am really anxious for some feedback.

I have the following fuction:
dxi/dt = k*qi*(xi-xj)/sqrt((xi-xj)^2+(yi-yj)^2+(zi-zj)^2)
where qi is the charge of the i-th particle, xi, yi, zi are the 
coordinates of the i-th particle and xj, yj,zj are the coordinates of the j-th 
particle. 
Input for the initial values: 
q[4] =  { 1.0, 1.0, -1.0, 1.0 } charge 
x0[4] = { 1.0, 2.3, 3.2, 4.0 } init posn x
y0[4] = { 1.0, 2.4, 3.0, 4.0 } init posn y
z0[4] = { 1.0, 2.5, 3.3, 4.2 } init posn z
QUESTION:
Since there are two values for each coordinate (i and 
j), how can I write the function in an acceptable form for RK4? 
I would appreciate any feedback concerning RK4.
Thanks for your time,
C.

       
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