Added nevilles algorithm for polynomial interpolation

maths/nevilles_method.py

@@ -0,0 +1,56 @@
+"""
+    Python program to show how to interpolate and evaluate a polynomial
+    using Neville's method.
+    Neville’s method evaluates a polynomial that passes through a
+    given set of x and y points for a particular x value (x0) using the
+    Newton polynomial form.
+    Reference:
+        https://rpubs.com/aaronsc32/nevilles-method-polynomial-interpolation
+"""
+
+
+def neville_interpolate(x_points: list, y_points: list, x0: int) -> list:
+    """
+       Interpolate and evaluate a polynomial using Neville's method.
+       Arguments:
+           x_points, y_points: Iterables of x and corresponding y points through
+            which the polynomial passes.
+           x0: The value of x to evaluate the polynomial for.
+       Return Value: A list of the approximated value and the Neville iterations
+           table respectively.
+    >>> import pprint
+    >>> neville_interpolate((1,2,3,4,6), (6,7,8,9,11), 5)[0]
+    10.0
+    >>> pprint.pprint(neville_interpolate((1,2,3,4,6), (6,7,8,9,11), 99)[1])
+    [[0, 6, 0, 0, 0],
+     [0, 7, 0, 0, 0],
+     [0, 8, 104.0, 0, 0],
+     [0, 9, 104.0, 104.0, 0],
+     [0, 11, 104.0, 104.0, 104.0]]
+    >>> neville_interpolate((1,2,3,4,6), (6,7,8,9,11), 99)[0]
+    104.0
+    >>> neville_interpolate((1,2,3,4,6), (6,7,8,9,11), '')
+    Traceback (most recent call last):
+      File "<stdin>", line 1, in <module>
+      ...
+    TypeError: unsupported operand type(s) for -: 'str' and 'int'
+    """
+    n = len(x_points)
+    q = [[0] * n for i in range(n)]
+    for i in range(n):
+        q[i][1] = y_points[i]
+
+    for i in range(2, n):
+        for j in range(i, n):
+            q[j][i] = (
+                (x0 - x_points[j - i + 1]) * q[j][i - 1]
+                - (x0 - x_points[j]) * q[j - 1][i - 1]
+            ) / (x_points[j] - x_points[j - i + 1])
+
+    return [q[n - 1][n - 1], q]
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()