I've made a program that solves non-linear systems (2x2 and 3x3) of equations by newton method: **r**[i+1]=**r**[i]-**J**(**r**[i])^-1***F**(**r**[i]).

The user is able to insert the functions (that I've set the program to store in FMEM - fn1, fn2...). During the iteration the values of each function will be in the vector **F**.

The big deal is defining the Jacobian Matrix. I wasn't able to find any way to make it unless the user insert by itself all the derivatives (4 or 9 functions) and the program allocate them, after calculating its values, in the matrix **J**.

Any suggestions or tips?