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Numerical Methods Tool

Interpolation Calculator

Find values between data points using linear, Lagrange, and Newton interpolation methods. Our calculator provides step-by-step solutions for numerical analysis, data fitting, and polynomial interpolation with detailed mathematical explanations.

Last updated: December 15, 2024

Multiple interpolation methods supported
Step-by-step solution process
Error estimation and accuracy analysis

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Interpolation Calculator
Find values between data points using various interpolation methods

Interpolation Result

Interpolated Value:

f(1.5) = 6.25

Using lagrange interpolation with 4 data points

Method Details:

Method: Lagrange
Polynomial Degree: 3
Data Points: 4
Error Estimate: ±0.3125

Interpolating Polynomial:

1.0000 × (x - 1)/(0 - 1) × (x - 2)/(0 - 2) × (x - 3)/(0 - 3) + 4.0000 × (x - 0)/(1 - 0) × (x - 2)/(1 - 2) × (x - 3)/(1 - 3) + 9.0000 × (x - 0)/(2 - 0) × (x - 1)/(2 - 1) × (x - 3)/(2 - 3) + 16.0000 × (x - 0)/(3 - 0) × (x - 1)/(3 - 1) × (x - 2)/(3 - 2)

Data Points Used:

X Values
Y Values
0
1
1
4
2
9
3
16

Quick Example Result

For data points (0,1), (1,4), (2,9), (3,16) interpolating at x = 1.5:

f(1.5) = 6.25

How This Calculator Works

Our interpolation calculator uses proven numerical methods to estimate values between known data points. The process involves constructing polynomials that pass through your data points and evaluating them at the target location. Each method offers different advantages for various types of data and accuracy requirements.

Interpolation Methods

Linear Interpolation:

f(x) = y₀ + (y₁ - y₀) × (x - x₀) / (x₁ - x₀)

Lagrange Interpolation:

P(x) = Σ yᵢ × Πⱼ≠ᵢ (x - xⱼ) / (xᵢ - xⱼ)

Newton's Method:

P(x) = f[x₀] + f[x₀,x₁](x-x₀) + f[x₀,x₁,x₂](x-x₀)(x-x₁) + ...
📈 Interpolation Visualization

Shows how different methods fit curves through data points

Mathematical Foundation

Interpolation is based on the Weierstrass approximation theorem, which states that any continuous function can be uniformly approximated by polynomials. Each method constructs a unique polynomial of degree n-1 that passes through n data points, providing different computational advantages and numerical properties.

  • Linear interpolation provides first-order accuracy with minimal computation
  • Lagrange method offers explicit polynomial form but can be numerically unstable
  • Newton's divided differences allow efficient addition of new data points
  • Higher-degree polynomials can suffer from Runge's phenomenon with many points

Sources & References

  • Numerical Recipes - Press, Teukolsky, Vetterling, and FlanneryComprehensive reference for numerical interpolation methods
  • Burden & Faires - Numerical Analysis TextbookStandard academic reference for interpolation theory
  • NIST Handbook - Mathematical Functions ReferenceGovernment standard for numerical computation methods

Need help with other numerical calculations? Check out our derivative calculator and quadratic formula calculator.

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Example Calculation

Real-World Example
Let's interpolate a value using Lagrange method

Given Data Points:

  • Point 1: (0, 1)
  • Point 2: (1, 4)
  • Point 3: (2, 9)
  • Point 4: (3, 16)
  • Target X: 1.5

Calculation Steps:

  1. Identify data points and target value
  2. Apply Lagrange interpolation formula
  3. Calculate each Lagrange basis polynomial
  4. Sum weighted contributions: f(1.5) = 6.25

Result: f(1.5) = 6.25

This interpolated value estimates the function at x = 1.5 based on the given data points.

Frequently Asked Questions

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