16.1 Interpolate/Extrapolate

See more related video:Origin VT-0010 Interpolation

1 Overview
- 1.1 To Interpolate/Extrapolate Your Data
2 Dialog Options
3 Algorithm
4 References

Overview

Interpolation/extrapolation is a method of estimating and constructing new data points from a discrete set of known data points. This function generates a uniform linearly spaced interpolated curve by one of four methods: Linear, Cubic Spline, Cubic B-Spline, and Akima Spline.

In Origin, the interpolation tool also supports Apparent Interpolation so it can interpolate data according to current axis settings.

To Interpolate/Extrapolate Your Data

Create a new worksheet with input data.
Select Analysis: Mathematics: Interpolate/Extrapolate.... This opens interp1XY dialog box.

The dialog box calls the interp1xy X-Function to perform the interpolate/extrapolate calculation.

Dialog Options

Recalculate	Controls recalculation of analysis results: None Auto Manual For more information, see: Recalculating Analysis Results
Input	Specifies the XY range to be interpolated. For help with range controls, see: Specifying Your Input Data
Method	Specify the interpolation/extrapolation method. Linear Linear interpolation is a fast method of estimating a data point by constructing a line between two neighboring data points. This method is generally less accurate than more computationally-intensive methods. Cubic Spline This method splits the input data into a given number of pieces, and fits each segment with a cubic polynomial. The second derivative of each cubic function is set equal to zero. With these boundary conditions met, an entire function can be constructed in a piece-wise manner. Cubic B-Spline This method also splits the input data into pieces, each segment is fitted with discrete Bezier splines. Akima Spline This method is based on a piecewise function composed of a set of polynomials. The Akima interpolation is stable to outliers.
Generate X Data by	It supplies two options for generating X Data Number of Points Specifies the number of interpolated points. Increment Specifies the increment when interpolate by Sampling Interval
X Start	The start X value of interpolated curve. Note: if want to generate a descending x data, you can X Start>X End.
X end	The end X value of interpolated curve. An Inverse button shows after the Auto checkbox to switch the values of X Start and X End.
Boundary	Boundary condition is only available in Cubic Spline method. Natural 2nd derivatives are 0 on both ends. Not-A-Knot 3rd derivatives are continuous on the second and last-second point.
Smoothing Factor	A non-negative parameter that specifies the smoothness of the interpolated curve in Cubic B-Spline interpolation. The factor helps user control the balance between the smoothing and closeness. Larger values will result in smoother curves. Smoothing is only available in Cubic B-Spline method.
Coefficients	Spline coefficients when using spline or B-spline method.
Apparent Interpolation	Available only when the interpolation is performed on a graph. If selected, interpolation is performed using apparent values when the axes scale type has been changed (from linear to log10, for instance).
Output	Specifies the output XY data range.