Below is a list of programs plus data that can be run using gnuplot. The gnuplot programs have a *.p extension. The data files have a *.txt extension. To run a program in gnuplot in terminal mode, type "gnuplot program.p". The programs listed below are used to find the best fit to data in the data file "*.txt" with a function f(x) that contains a certain number of free parameters.

• The program fitdata.p finds a best fit to the data sampledata.txt. The fit function in fitdata.p is f(x) = k1 + k2*x*x. The free parameters in the fit are k1 and k2. The best fit parameters are printed on the screen and the program also produces a graph of the data and fit in *.pdf format.
• The program fitsteelcool.p finds a best fit to the data steelcool.txt. The data are the difference in temperature of steel and water as the steel cools down. The fit function in fitsteelcool.p is f(x) = T0*exp(-g*x). The free parameters in the fit are T0 and g. For gnuplot to find a good fit, you need to supply initial non-zero starting values for the search. The program produces a graph of the data and fit in *.pdf format.
• The program fitfree_oscill.p finds a best fit to the data dampdat.txt. The program can be used to fit the data of an undriven damped oscillator subject to a linear restoring force and a linear resistance force. The fitting equation is f(x) = a*exp(-b*x)*cos(6.28319*x/T+p). f(x) is the amplitude at a time x, and there are four parameters for the fit: a, b, T, and p. You will need to supply non-zero initial starting values of these four parameters for gnuplot to find a reasonable fit.
• For the case of the overdamped oscillator, one can use the gnuplot code overdamped.p, For the critically damped situation, the code critdamped.p, can be used. In each case, be sure you have the correct input data file and starting values for the parameters.

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