Add inverse_quad_interp

Author: onezerosix

inverse_quad_interp.m

@@ -0,0 +1,31 @@
+function [x] = inverse_quad_interp(x, func)
+% INVERSE_QUAD_INTERP Gives the result of interpolating the given function
+% by the inverse quardatic method once and can continue interpolating until
+% the user says to stop.
+%
+% INPUT
+% x: the first three x values to use for interpolating
+% func: the function to use
+%
+% OUTPUT
+% x: the final three values of x (after user says to stop interpolating)
+
+keep_looping = 1;
+
+while keep_looping ~= 0
+    y = [func(x(1)) func(x(2)) func(x(3))];
+
+    % calculate gamma, alpha, beta
+    gamma = (x(1) - x(3)) / (y(1) - y(3));
+    alpha = (x(1) - x(2)) / (y(1) - y(2));
+    beta = (alpha - gamma) / (y(2) - y(3));
+
+    % compute next estimates
+    nextX = x(1) - alpha*y(1) + beta*y(1)*y(2);
+    x = [nextX, x(1), x(2)];
+    
+    disp(x);
+    keep_looping = input('To stop interpolating, type 0, else 1: ');
+end
+
+end