Jan 30, 2002 ------------ - New topic: interpolation - Examples - Driving from C'burg to Roanoke on I-81 - weather maps - niceness and grades - There are several choices for interpolating polynomials - if we insist on lowest degree <=n, we can get uniqueness - Statement of uniqueness theorem - Two different forms for the interpolating polynomial - Lagrange form - Newton form - Finding Newton's form by divided differences table - what happens if you change order of entries? - what does it mean when you have zeros in a column? - Worked out exercise 4.1.15 from textbook - Notice the difference between saying - "the data comes from a cubic polynomial", and - "the lowest order polynomial is a cubic" Feb 4, 2002 ------------ (one class in between went for MATLAB) - Continue on interpolation and doodling - Just more problem solving in class; solved - 4.1.18 - 4.1.19 - 4.1.22 - 4.1.23 - 4.1.26 Feb 6, 2002 ------------ - Revisit Lagrange and Newton forms - Lagrange form is not `incremental' when you get additional data - Newton form is `incremental' - Specializations of Newton form - centers are same: shifted power form - how do you determine the coefficients? - centers are same and zero: power form - Why all these forms? - what is the advantage? - Connection between divided difference table and derivatives - Recap: interpolation finds a polynomial passing through given points - what about non-nodal points? - Pathological example with 1/(1+x^2) Feb 8, 2002 ------------ - Continued pathological example - problem is equally spaced nodes - Chebyshev nodes in [-1,1] - Mapping Chebyshev nodes to [a,b] - Moral of the story - Use Chebyshev nodes, or (take this on faith for now) - Use equally spaced nodes (but don't go too far from center of range) - Errors in Interpolation - Interpolation Errrors Theorem - Example: error in linear interpolation - Specializing the theorem to equally spaced nodes - Solved problems - example 1 from section 4.2 - problem 4.2.9 (page 170) - but we assumed equally spaced nodes