i'm a pretty inexperienced programmer and am trying to use BI from chapter 3.6.

I understand how to get the first and second derivatives from using centred differencing but then in NR i ssays to get the values c[i][j] using bucuof routine which i dont understand at all how to get them. also if i founf these values how would i be able to get y(x1,x2) ??

Hi Mike,

The answer of ur question is quite simple. One has 16 coefficient and 4 equations. If u have 4 tabulated points , u can just build 4x4=16 equations to solve ur coefficients...
After u have these coefficients u can use the first equation to calculate the values at the wanted coordinates. 't' and 'u' can be calculated through ur coordinates