kevbot is on to something here. The two systems use rather different methods for fitting the data.

Statistics::LineFit and LibreOffice are doing a standard linear least squares fit. This is not an iterative process and is not dependent on any initial guesses.

The Gnuplot documentation for fit says that it uses a nonlinear least-squares (NLLS) Marquardt-Levenberg algorithm.

In reply to Re: Statistics::LineFit versus gnuplot, results differ by sn1987a
in thread Statistics::LineFit versus gnuplot, results differ by neilwatson

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