Lagrangian Interpolation Chemical Engineering Majors Authors: Autar Kaw, Jai Paul http://numericalmethods.eng.usf.edu Transforming Numerical Methods Education for STEM Undergraduates http://numericalmethods.eng.usf.edu
Lagrange Method of Interpolation http://numericalmethods.eng.usf.edu
What is Interpolation ? Given (x0,y0), (x1,y1), …… (xn,yn), find the value of ‘y’ at a value of ‘x’ that is not given. http://numericalmethods.eng.usf.edu
Interpolants Evaluate Differentiate, and Integrate. Polynomials are the most common choice of interpolants because they are easy to: Evaluate Differentiate, and Integrate. http://numericalmethods.eng.usf.edu
Lagrangian Interpolation http://numericalmethods.eng.usf.edu
Example To find how much heat is required to bring a kettle of water to boiling point, you are asked to calculate the specific heat of water at 610C. Use a first, second and third order Lagrange polynomial to determine the value of the specific heat at T = 61°C. Table 1 Specific heat of water as a function of temperature. Temperature, Specific heat, 22 42 52 82 100 4181 4179 4186 4199 4217 Figure 2 Specific heat of water vs. temperature. http://numericalmethods.eng.usf.edu
Linear Interpolation http://numericalmethods.eng.usf.edu
Linear Interpolation (contd) http://numericalmethods.eng.usf.edu
Quadratic Interpolation http://numericalmethods.eng.usf.edu
Quadratic Interpolation (contd) http://numericalmethods.eng.usf.edu
Quadratic Interpolation (contd) http://numericalmethods.eng.usf.edu
Cubic Interpolation http://numericalmethods.eng.usf.edu
Cubic Interpolation (contd) http://numericalmethods.eng.usf.edu
Cubic Interpolation (contd) http://numericalmethods.eng.usf.edu
Cubic Interpolation (contd) The absolute relative approximate error obtained between the results from the second and third order polynomial is http://numericalmethods.eng.usf.edu
Comparison Table http://numericalmethods.eng.usf.edu
Additional Resources For all resources on this topic such as digital audiovisual lectures, primers, textbook chapters, multiple-choice tests, worksheets in MATLAB, MATHEMATICA, MathCad and MAPLE, blogs, related physical problems, please visit http://numericalmethods.eng.usf.edu/topics/lagrange_method.html
THE END http://numericalmethods.eng.usf.edu