pybacktrack.read_interpolate_function

pybacktrack.read_interpolate_function(curve_filename, x_column_index=0, y_column_index=1, *, out_of_bounds='clamp')

Read x and y columns from a curve file and return a function y(x) that linearly interpolates.

Parameters:

• curve_filename (string) – Name of input text file containing the x and y data from which to create the returned curve function.

• x_column_index (int, optional) – Determines which column of input text file to read x values from.

• y_column_index (int, optional) – Determines which column of input text file to read y values from.

• out_of_bounds (string, optional) –

  Determines the y value returned by curve function when x is outside the range of x values in curve file. This can be:

  • clamp to return the boundary y value, or

  • exclude to return None (eg, to indicate that there’s no y value), or

  • extrapolate to return an extrapolated value.

Returns:

• curve_function (function) – A callable function y=f(x) accepting a single x argument, and returning a y value or None (if no y value).

• x_column (list of float) – The x values read from the curve file.

• y_column (list of float) – The y values read from the curve file.

Raises:

• ValueError – If cannot read x and y columns, as floating-point numbers, from the curve file at column indices x_column_index and y_column_index.

• ValueError – If curve file contains no data.

• ValueError – If out_of_bounds is not clamp, exclude or extrapolate.

Notes

The returned x and y columns are useful if integrating the curve function with scipy.integrate.quad (since can pass x column to its points argument and len(x) to its limit).

Changed in version 1.5: The following changes were made:

• Added out_of_bounds argument. If out_of_bounds is exclude then returned curve function will return None for any input x outside the range of x values in curve file.

• Some arguments (after *) are now keyword-only (ie, can no longer be specified as positional arguments).