Interpolation Calculator

Comma-separated. They do not need to be sorted or evenly spaced.
An x value normally; a y value when solving in reverse.
Inverse interpolation uses the piecewise-linear method.
Interpolated value
4
Interpolation Calculator
Method
linear
Interval used
[1, 3]
Slope of the segment
2
Interpolating polynomial
2x
Outside the data range
no
Points used
2
Worked out from Burden & Faires, Numerical Analysis, chapter 3 (Interpolation and Polynomial Approximation) and 1 other source.

How this is worked out

3 steps
  1. Bracketing points: (1, 2) and (3, 6).
  2. Slope = (6 - 2) / (3 - 1) = 2.
  3. Value = 2 + 2 x (2 - 1) = 4.
Polynomial coefficients (ascending powers)table
0, 2

Results are general information, not financial, tax, legal, medical or engineering advice.