def ndist(data,Xs):
sigma=np.sqrt(np.var(data))<EOL>center=np.average(data)<EOL>curve=mlab.normpdf(Xs,center,sigma)<EOL>curve*=len(data)*HIST_RESOLUTION<EOL>return curve<EOL>
given some data and a list of X posistions, return the normal
distribution curve as a Y point at each of those Xs.