83 lines
2.6 KiB
Python
Executable File
83 lines
2.6 KiB
Python
Executable File
#!/usr/bin/env python
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#-*- coding:utf-8 -*-
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class Interpolator:
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def __init__(self):
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self._indexes = []
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self._values = []
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self._sorted = False
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self.methods = {"linear": self._interpolate_linear}
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def add_value(self, index, value):
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if type(index) not in (int, float) or type(value) not in (int, float):
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try:
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index = float(index)
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value = float(value)
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except ValueError:
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raise TypeError(f"Interpolator.add_value: index '{index}' or value '{value}' not a number")
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self._indexes.append(index)
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self._values.append(value)
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self._sorted = False
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def add_values(self, indexes, values):
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for i, v in zip(indexes, values):
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self.add_value(i, v)
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def interpolate(self, index, extrapolate=True, method="linear", sort=True):
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if not method in self.methods:
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raise NotImplementedError(f"Interpolator.interpolate: interpolation method '{method}' not yet supported")
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if len(self._indexes) < 2:
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raise ValueError(f"Interpolator.interpolate: cannot interpolate on a table with less than two data points")
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# only sort if not already sorted to increase performance for large tables
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if not self._sorted and sort:
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self._indexes.sort()
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self._values.sort()
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self._sorted = True
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return self.methods[method](index, extrapolate)
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def _find_neighbours(self, index):
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lower = upper = 0
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last = self._indexes[0]
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for it, _index in enumerate(self._indexes):
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lower = last
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last = it
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if _index > index:
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upper = it
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break
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return lower, upper
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def _interpolate_linear(self, index, extrapolate=True):
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if index in self._indexes:
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return self._values[self._indexes.index(index)]
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if self._indexes[0] < index < self._indexes[-1]:
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lower, upper = self._find_neighbours(index)
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return self._values[lower] + (self._values[upper] - self._values[lower]) * (index - self._indexes[lower]) / (self._indexes[upper] - self._indexes[lower])
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else:
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if not extrapolate:
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if index < self._indexes[0]:
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return self._values[0]
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else:
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return self._values[-1]
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else:
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if index < self._indexes[0]:
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return self._values[1] + (index - self._indexes[1]) / (self._indexes[0] - self._indexes[1]) * (self._values[0] - self._values[1])
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else:
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return self._values[-2] + (index - self._indexes[-2]) / (self._indexes[-1] - self._indexes[-2]) * (self._values[-1] - self._values[-2])
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# run test if run directly
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if __name__ == "__main__":
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print("Test results")
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i = Interpolator()
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i.add_values((0, 10, 20), (0, 20, 30))
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for test_val in (-5, 0, 1, 2, 3.5, 5.55555, 9, 10, 15, 100):
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print(test_val, i.interpolate(test_val))
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