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Full Version: cubic spline "fit" and interpolation of tabular data
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This HP Prime program demonstrates how to interact with cubic spline subroutines which "fit" and interpolate two-dimensional tabular data of the form y = f(x).

The following statement defines the total number of x-y data pairs

// define number of x and y data pairs

EXPORT ndata := 168;

The x and y data pairs are provided by the user in EXPORT data statements of the form

// x-data array (calendar date)

EXPORT xdata :=[1994.917,1995.0004,1995.0836,1995.167,1995.2504,1995.3336,1995.417,1995.5004,199​5.5836,1995.667, .....

// y-data array (solar flux)

EXPORT ydata := [80.4,79.6,78.8,78.2,77.7,77.3,76.7,76,75.3,74.5,73.7,73.2,72.9,72.5,72.3,72.2,72​.1,72.1,72.3,72.6,72.9, .....

The user provides the x value for interpolation in a statement with the following format

xval := 2006.0;

The software and documentation for this program can be downloaded from

Reference URL's