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Numerical Analysis

Error, root-finding, interpolation, and numerical linear algebra/ODEs -- the practical algorithms behind approximate solutions, and why they work.

Free to read now, no account needed: Readiness: what numerical analysis leans on. Create a free account to open the other chapters, take the quizzes and keep your progress.

1 Foundations of Numerical Computing πŸ”’

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  • Exact vs. approximate solutions ~10 min
  • Algorithms, convergence, and rate of convergence ~11 min
  • Sources of error: round-off and truncation ~10 min
  • Absolute error, relative error, and significant digits ~12 min
  • Floating-point representation and machine epsilon ~13 min
  • Overflow, underflow, and rounding modes ~11 min
  • Catastrophic cancellation and loss of significance ~12 min
  • Conditioning: how sensitive is the problem? ~13 min
  • Stability: how sensitive is the algorithm? ~13 min

2 Root-Finding for Nonlinear Equations πŸ”’

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  • Bracketing a root: the Intermediate Value Theorem in practice ~12 min
  • The Bisection Method ~16 min
  • Fixed-point iteration and the cobweb diagram ~14 min
  • Convergence of fixed-point iteration: the contraction condition ~14 min
  • Newton's Method: derivation from the tangent line ~16 min
  • Newton's Method: convergence order and failure modes ~15 min
  • The Secant Method ~14 min
  • The Method of False Position ~13 min
  • MΓΌller's Method and roots of polynomials ~15 min
  • Choosing a root-finding method ~12 min

3 Polynomial Interpolation πŸ”’

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  • The interpolation problem: existence and uniqueness ~13 min
  • The Lagrange form of the interpolating polynomial ~15 min
  • Newton's divided-difference form ~18 min
  • Neville's method ~14 min
  • The interpolation error formula ~15 min
  • Equally spaced nodes and the Runge phenomenon ~16 min
  • Chebyshev nodes: taming the Runge phenomenon ~15 min
  • Hermite interpolation ~15 min
  • Extrapolation: why it's riskier than interpolation ~13 min

4 Spline Interpolation πŸ”’

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  • Why one high-degree polynomial can go wrong ~12 min
  • Piecewise linear and piecewise quadratic splines ~15 min
  • Cubic splines: setting up the system ~20 min
  • Natural boundary conditions ~22 min
  • Clamped boundary conditions ~18 min
  • Continuity of position, slope, and curvature ~16 min
  • Solving the spline system: tridiagonal solvers ~17 min
  • Parametric curves from splines ~15 min

5 Numerical Differentiation πŸ”’

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  • Forward and backward difference formulas ~14 min
  • The central difference formula ~14 min
  • Deriving difference formulas from Taylor series ~18 min
  • Truncation error vs. round-off error in differentiation ~16 min
  • Choosing the step size h: the U-shaped error curve ~18 min
  • Richardson extrapolation ~20 min

6 Numerical Integration πŸ”’

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  • The midpoint and trapezoidal rules: error bounds ~14 min
  • Simpson's rule and degree of precision ~20 min
  • Composite rules and error bounds ~18 min
  • Romberg integration ~18 min
  • Adaptive quadrature ~16 min
  • Gaussian quadrature: nodes and weights ~18 min
  • Improper integrals, numerically ~14 min
  • Multiple integrals, briefly ~12 min
  • Trigonometric approximation and the idea of the FFT ~12 min
  • Choosing a quadrature method ~12 min

7 Direct Methods for Linear Systems πŸ”’

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  • Gaussian elimination, revisited numerically ~10 min
  • Partial pivoting and why it's necessary ~20 min
  • Operation counts: why elimination is $O(n^3)$ ~12 min
  • LU factorization from elimination ~15 min
  • Cholesky factorization for symmetric positive-definite systems ~15 min
  • Vector and matrix norms ~14 min
  • The condition number of a matrix ~16 min
  • Iterative refinement ~14 min
  • Special matrix structures: banded and tridiagonal systems ~14 min

8 Iterative Methods for Linear Systems πŸ”’

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  • Why iterate instead of solving directly? ~11 min
  • The Jacobi method ~18 min
  • The Gauss-Seidel method ~15 min
  • Successive over-relaxation (SOR) ~16 min
  • Convergence: diagonal dominance and spectral radius ~17 min
  • The Conjugate Gradient method ~17 min
  • Direct vs. iterative: choosing a method ~12 min

9 Least Squares and Curve Fitting πŸ”’

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  • Overdetermined systems and the least-squares problem ~14 min
  • The normal equations ~14 min
  • Why the normal equations can be numerically dangerous ~18 min
  • Least squares via QR factorization ~20 min
  • Polynomial and nonlinear curve fitting ~16 min
  • Orthogonal polynomials as a stable fitting basis ~16 min
  • Residuals and goodness of fit ~15 min

10 Numerical Eigenvalue Problems πŸ”’

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  • Why not just use the characteristic polynomial? ~12 min
  • The Power Method ~16 min
  • The Rayleigh quotient and accelerated convergence ~20 min
  • The Inverse Power Method and Shifted Inverse Iteration ~18 min
  • Deflation ~16 min
  • Householder Reflections and Reduction to Hessenberg Form ~18 min
  • The QR Algorithm ~20 min
  • Computing the SVD Numerically ~18 min
  • Choosing an Eigenvalue Method ~14 min

11 Numerical Solutions of Nonlinear Systems πŸ”’

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  • Fixed Points for Functions of Several Variables ~16 min
  • Newton's Method for Systems: the Jacobian ~22 min
  • Quasi-Newton (Broyden's) Methods ~18 min
  • Steepest Descent as a Globalization Strategy ~18 min
  • Homotopy and Continuation Methods ~18 min
  • Golden-Section Search: the One-Dimensional Case ~16 min

12 Initial-Value Problems for ODEs πŸ”’

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  • Well-posedness of the initial-value problem, revisited ~14 min
  • Euler's method, revisited numerically ~15 min
  • Local vs. global truncation error, made formal ~20 min
  • Higher-order Taylor methods ~16 min
  • Runge-Kutta methods: RK2 and the midpoint method ~18 min
  • RK4 ~22 min
  • Adaptive step size: the Runge-Kutta-Fehlberg method ~20 min
  • Multistep methods: Adams-Bashforth and Adams-Moulton ~20 min
  • Predictor-corrector methods ~16 min
  • Absolute stability and stiff equations ~24 min
  • Systems and higher-order equations ~18 min

13 Boundary-Value Problems for ODEs πŸ”’

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  • What makes a BVP different from an IVP ~16 min
  • The Linear Shooting Method ~22 min
  • The Shooting Method for Nonlinear Problems ~20 min
  • Finite-Difference Methods for BVPs ~20 min
  • The Rayleigh-Ritz Method, Briefly ~14 min

14 A Survey of Numerical Methods for PDEs πŸ”’

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  • Classifying PDEs for numerical purposes ~16 min
  • Finite differences for the heat equation, revisited ~14 min
  • Finite differences for the wave equation, revisited ~14 min
  • Finite differences for Laplace's equation, revisited ~16 min
  • Choosing a numerical PDE method ~14 min
  • Capstone: building a numerical solution end to end ~22 min