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lagrange_interpolation.m

+%Lagrange's interpolation
+%clear all
+% Interpolating data by Lagrange's method
+%input 
+
+
+function yp  = LAGRANGE_S(n, x, y, xp)
+%main program
+    L = zeros(n);
+    for i =1:n
+        L(i)=1; 
+        for j =1:n
+            if (i~=j)
+               L(i)= L(i)*(xp-x(j))/(x(i)-x(j));
+            end
+        end
+    end
+    yp=y*L';
+    %ouput 
+    %fprintf('the required value of y at xp is %f',yp)
+
+    % Note: To see the data with multipliers use the follwoing 2 liines
+    %fprintf('x    y    L   y.*L\n') 
+    table = [x;y;L; y.*L]'; 
+
+%---------------------------------------------------------------------
+% OUTPUT 1
+% enter the no. of data points = 5
+% enter the x values as a row matrix [1 2 3 4 5]
+% enter the y values as a row matrix [2 4 10 15 20]
+% enter the x value for which y is to be evaluated = 1.5
+% the required value of y at xp is 1.953125>> 
+
+%---------------------------------------------------------------------
+% OUTPUT 1
+% enter the no. of data points = 5
+% enter the x values as a row matrix [1 2 3 4 5]
+% enter the y values as a row matrix [2 4 10 15 20]
+% enter the x value for which y is to be evaluated = 3.5
+% the required value of y at xp is 12.703125>> 
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