From Numerical Analysis 10-10-18

LagrangeInterpolation.m

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+function [value] = LagrangeInterpolation(x_data, y_data, x)
+%LagrangeInterpolation evaluates the lagrange interpolation polynomial for
+%given set of data points
+%
+%   Input
+%       - x_data: One-dimensional list of x-coordinates of point through
+%       which the interpolating polynomial will pass. The degree of the
+%       interpolating polynomial, n, will be inferred from the number of
+%       entries in x_data
+%       - y_data: One-dimensional list of y-coordinates of point through
+%       which the interpolating polynomial will pass
+%       - x: One-dimensional list of values for which the Lagtrange
+%       polynomial will be evaluated
+%
+%   Output
+%       - value: Value(s) of interpolation polynomial
+
+    %Ensure that the y_data list is a row vector
+    y_data = y_data(:)';
+    
+    %Do the interpolation
+    value = y_data*LagrangePolynomials(x_data, x);
+end
+