# 16.3 Trace Interpolation

## Overview

Trace Interpolation is different from ordinary interpolation since it interpolates the curve based on the index of X coordinate rather than adjacent data points in the X coordinate. When the curve is cyclic or periodic, it is more appropriate to use trace interpolation rather than ordinary interpolation. Choose from one of three methods: Linear, Cubic Spline and Cubic B-Spline.

##### To Perform Trace Interpolation
1. Select Analysis: Mathematics: Trace Interpolate. This opens interp1trace dialog.
2. Specify the Input and desired Method as well as Number of Points.
3. Upon clicking OK, two new columns of interpolated X and Y values are added to the source worksheet.

## Dialog Options

Recalculate Controls recalculation of analysis results None Auto Manual For more information, see: Recalculating Analysis Results Specifies the XY range to be interpolated. For help with range controls, see: Specifying Your Input Data 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. The number of interpolated points. Specifies the output XY data range

## Algorithm

For more specific information on tool usage or on the specifics of the algorithms used, see the documentation provided for the X-Function interp1trace in the Origin X-Function Help file (Help: X-Functions, or press the F1 key while the dialog box is open).