# 2.8.12 interp1trace

Analysis: Mathematics: Trace Interpolation

## Brief Information

Perform trace/periodic interpolation of XY data

## Command Line Usage

 

1. interp1trace iy:=Col(2) method:=spline npts:=50; 

2. interp1trace iy:=Col(2) method:=bspline; 

## Variables

Display
Name
Variable
Name
I/O
and
Type
Default
Value
Description
Input iy

Input

XYRange

<active>

The XY range to be interpolated.

Method method

Input

int

linear

Specifies the interpolation method.
Option list

• linear:Linear
Use linear interpolation method.
• Cubic spline
Use cubic spline interpolation method.
• Cubic B-spline
Use cubic B-spline interpolation method.
Number of Points npts

Input

int

<auto>

Specifies the number of interpolated points. If npts is not specified, default <auto> = min( n*5, 1000), where n is the number of input points. i.e. if number of points n is less than 200, npts=5*n, otherwise npts=1000.

Output oy

Output

XYRange

<new>

The XY range of interpolation result.

See the syntax here.

## Description

When a curve is cyclic, or periodic, it is improper to use ordinary interpolation because the algorithm interpolates the curve based on adjacent data points in the X coordinate. This causes the cycle trend to be lost.

This function interpolates a curve and keeps the trend.

## Examples

1. Import the file \Samples\Mathematics\ Circle.dat.

2. Highlight the data and plot a scatter.

3. Select Analysis: Mathematics: Trace Interpolation from menu to bring up the dialog.

4. Select Cubic B-spline interpolating method, and enter 50 on the Number of Points edit box.

5. Click OK to execute.

## Algorithm

Detail algorithms please refer to the help of interp1.

## Related X-Functions

Keywords:interpolate, extrapolate