Interpolation of data
This option will present you with a dialogue containing two tabs. The Single values tab is shown below. This allows you to enter an X value, and either entering RETURN or clicking Calculate will calculate the corresponding Y value using the fitted equation as plotted in the graph.
Note that you are allowed to extrapolate values outwith the range of the data for linear plots (least squares fits). You cannot extrapolate beyond the limits of the data fitted for any of the non-linear fits (eg polynomial) as the values produced are highly unpredictable.
The Range of values tab is shown below. This allows you to enter a start value, an end value, and an increment which will be used in the calculation. No extrapolation is allowed. Clicking Save or pressing RETURN will result in a Save as dialogue. The text file, containing the results of the calculation can then be saved to disc or transferred to a suitable application. The options Verbose output and Comma separate values control how the output is formatted, and what is included. Comma separated gives the simplest output - the x and y values with a comma separator, otherwise the values are tabbed into fields padded with spaces. Verbose output includes additional information such as the equation fitted and the parameters found.
Here is an example of verbose output.
Interpolation of data from parabola fit --------------------------------------- Equation fitted: Y = a + bx + cx^2 a = -43.6253 b = 3.91748 c = -0.0110847 X value Y value ------- ------- 20 30.29 30 63.923 40 95.338 50 124.54 60 151.52 70 176.28 80 198.83