Hi all, I have a problem that has made me scratch my head for many hours now! It might be something obvious that I am missing. I have a Newton-Raphson code to solve a system of nonlinear equations. The error that I get here does not have anything to do with the algorithm, but just to be clear, I need to find the best possible solution if the equations are not solvable, so I am trying to stop simulation when the direction found by Newton-Raphson is not correct! In order to do that I put an if-loop in the beginning of the main loop to take x from the previous iteration (x_previous), but I get x_previous not defined! I am using the Optim package to do a line search after the direction has been found by Newton-Raphson. If Optim is not used, things work perfectly (I tried by commenting out those lines of code). Otherwise I get the error I mentioned. My code is here: https://gist.github.com/prezaei85/372bde76012472865a94, which solves a simple one-variable quadratic equation. Any thoughts are very much appreciated.
Thanks, Pooya
