I am not going to reverse engineer your code, but it looks like your writing your own least-squares fitting algorithm and doing some simple plots. Also, from your many posts last days, it looks like you are a newbie struggling with a python interface to gnuplot.
May I suggest that you have a look at numpy/scipy/matplotlib instead? With those, the things that you are trying to do could be done trivially in a just a few lines. What you want to do could be done with something like (untested!): from pylab import * xdata = ... %whatever you get it from ydata = ... p = polyfit(xdata, ydata, 1) %fit 1st order polynomial plot(xdata, ydata, xdata, 'o', polyval(p, xdata)) %plot original data with fit show() Things like fitting algorithms are already included, so you can focus your energy on the real work. E.g., if you later want to change to a quadratic fit instead of a linear, you just change 1 to 2 in the polyfit. As you said in one of your other posts, you need to find the intersection point of two lines. If poly1 and poly2 are the polynomials describing the lines, you would get your answer as x_intersect = roots(poly1 - poly2) y_intersect = polyval(poly1,x_intersect) plot(x,polyval(poly1,x),x,polyval(poly2,x),x_intersect,y_intersect,'o') show() HTH, Bas -- http://mail.python.org/mailman/listinfo/python-list
