Hey again all,
I know it's a terribly late response, but I just wanted to thank you all for the answers and helping me out.
I have only taken Calc 2, and am not yet familiar with what/how to use an interpolating spline. I'm looking into that now. The the vector I am storing my missile's x location in is ~ 3000 elements. The actual values of the elements range from 0 to 300000. I will have to further experiment with polyfit... I was aware that my polyfit function might oscillate between the test points, but when I plotted it, I failed to add points to plot between the original test points. Thanks for bringing this up again...
Like I said, just wanted to thank you all for the help. This program was my final project, and I was looking for answers quick. Got destroyed with a ton of work and soon I'm responding a month later... I am still investigating this issue, so I will try and update this when I have investigated/experimented with my program more.