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SRS1 Cubic Spline for Excel V2.6 Released - Free Software Adds Expanded Spline and Linear Interpolation functions to Microsoft Excel... more...###### Related Products...

- Data Curve Fit Creator Add-in - Add curve fitting, splines, data smoothing functions directly to Microsoft Excel...

## SRS1 Cubic Spline for Excel

"Free software that adds cubic and other spline functions as well as linear interpolation to Microsoft Excel..."

Cubic Spline function

Constrained Spline functions

Linear Interpolation function

Simple to use; works like any other Microsoft Excel function

Totally Free

**Add multiple FREE spline interpolations functions to Microsoft Excel...**

SRS1 Cubic Spline for Excel adds several spline and linear interpolation functions to Microsoft Excel. The cubic spline function smoothly interpolates between given data points. Bessel and OneWay (monotonic) spline functions provide a more constrained smooth fit to data. A linear interpolation function is also included. The functions are accessed just like any other standard Excel function.

The latest version of SRS1 Cubic Spline for Excel supports Excel 2010 or later, including both 32 and 64 bit versions of Excel.

__Operating Systems Supported__: Windows 11, Windows 10, Windows 8.1, Windows 8, Windows 7, Server 2023, Server 2016, Server 2012

How to Use Cubic Spline Function in Excel (V2.5)
- This quick set of screen shots and explanation show you how to access the Cubic Spline functions in Excel. This explanation is valid for the versions 2.5 of SRS1 Cubic Spline for Excel or later.

Sample Excel Workbook Demonstrating Cubic Spline Functions in Excel (V2.5 or later)
- This workbook shows examples of how to use the functions in SRS1 Cubic Spline for Excel. This is sample workbook was made using the version 2.5 of the SRS1 Cubic Spline for Excel.

Real World Example: Interpolate monthly economic values from quarterly data
- This workbook shows a real world example of how the cubic spline function can be used to interpolate monthly values from a set of economic values that are given on a quarterly basis. Using a cubic spline is a common way to accomplish this, and being able to do this all directly in Microsoft Excel makes the task much easier. (Note: Uses v2.5 or later of SRS1 Cubic Spline for Excel.)

#### Video Demos

Using SRS1 Cubic Spline for Excel - This video tutorial shows how to use SRS1 Cubic Spline for Excel. It demonstrates how to use the cubic spline and linear interpolation functions that are added to Microsoft Excel.

For your support, see the downloaded workbook and the Frequently Asked Questions listed below here...

(1) What functions are included in the software? How do I access them?

(2) When I open a workbook created with the previous version of SRS1 Cubic Spline for Excel, I get some function errors. What can I do about that?

(3) Can I use 'SRS1 Cubic Spline for Excel' and 'Data Curve Fit Creator' at the same time?

(4) How does a cubic spline work?

(5) My cubic spline curve is very erratic and 'wobbles' quite a bit. How can I make the curve smoother?

(6) If I create a workbook using the spline function and then give the workbook to someone else, then will it work for them?

(7) What is the Bessel Spline and when would I use it?

(8) What is the OneWay Spline and when would I use it?

(9) What does 'monotonic' mean?

(10) Where else can I learn about implementing Cubic Splines?

(2) When I open a workbook created with the previous version of SRS1 Cubic Spline for Excel, I get some function errors. What can I do about that?

(3) Can I use 'SRS1 Cubic Spline for Excel' and 'Data Curve Fit Creator' at the same time?

(4) How does a cubic spline work?

(5) My cubic spline curve is very erratic and 'wobbles' quite a bit. How can I make the curve smoother?

(6) If I create a workbook using the spline function and then give the workbook to someone else, then will it work for them?

(7) What is the Bessel Spline and when would I use it?

(8) What is the OneWay Spline and when would I use it?

(9) What does 'monotonic' mean?

(10) Where else can I learn about implementing Cubic Splines?

(1) What functions are included in the software? How do I access them?

(2) When I open a workbook created with the previous version of SRS1 Cubic Spline for Excel, I get some function errors. What can I do about that?

(3) Can I use 'SRS1 Cubic Spline for Excel' and 'Data Curve Fit Creator' at the same time?

(4) How does a cubic spline work?

(5) My cubic spline curve is very erratic and 'wobbles' quite a bit. How can I make the curve smoother?

(6) If I create a workbook using the spline function and then give the workbook to someone else, then will it work for them?

(7) What is the Bessel Spline and when would I use it?

(8) What is the OneWay Spline and when would I use it?

(9) What does 'monotonic' mean?

(10) Where else can I learn about implementing Cubic Splines?

Version 2.6 has four functions: 'linear_interp', 'cubic_spline', 'bessel_spline' and 'oneway_spline'. These functions are listed under the 'SRS1Spline.Functions25' function category in the 'Insert Function' dialog box of Excel.

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(2) When I open a workbook created with the previous version of SRS1 Cubic Spline for Excel, I get some function errors. What can I do about that?

Click the Repair/Refresh button on the ribbon bar to refresh the functions on your workbook and fix those broken links.

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(3) Can I use 'SRS1 Cubic Spline for Excel' and 'Data Curve Fit Creator' at the same time?

Yes. 'Data Curve Fit Creator Add-in' has all the functions included in SRS1 Cubic Spline for Excel along with many more. To avoid confusion, the function names in SRS1 'SRS1 Cubic Spline for Excel' include underscores, but the function names in Data Curve Fit Creator Add-in do not contain underscores.

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(4) How does a cubic spline work?

A cubic spline interpolates a smooth line through a given set of data points. Unlike a polynomial or other curve fits, a spline is forced to directly pass through all points in the dataset. There are a few other constraints that are used to generate the smooth curve. The second derivative of the interpolated curve will vary linearly between source data points. Also, the first derivative of the curve needs to be continuous across the curve.

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(5) My cubic spline curve is very erratic and 'wobbles' quite a bit. How can I make the curve smoother?

As mentioned before, the cubic spline is forced to go through all data points. If there is noise in your data, then the curve can become erratic as it tries to smoothly pass through each point. You can try using the Bessel_spline or OneWay_spline functions for more constrained results.

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(6) If I create a workbook using the spline function and then give the workbook to someone else, then will it work for them?

The other person needs to have the SRS1 Cubic Spline for Excel add-in installed on their machine for functions to work for them.

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(7) What is the Bessel Spline and when would I use it?

The Bessel spline is similar to the cubic spline except the Bessel spline uses a parabolic fit internally for its interpolation. The results of the Bessel spline can be more constrained (fewer unwanted oscillations) than the cubic spline, but might be be as smooth.

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(8) What is the OneWay Spline and when would I use it?

The 'OneWay' spline is a constrained version of the bessel spline which always produces monotic results as long as the source data is monotonic. It is the most constrained (fewest overshoots and oscillations) spline in this add-in. You can use the OneWay spline with data that isn't monotonic as well. In that case the results won't necessarily be monotonic, but it will still be a very contrained curve (fewest possible overshoots and oscillations). You would use this if you had monotonic data or if the other splines produced oscillations between data points.

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(9) What does 'monotonic' mean?

It means only flat/increasing or only flat/decreasing. For example {1,2,2,3} is monotonic while {1, 2, 3, 2} is not.

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(10) Where else can I learn about implementing Cubic Splines?

We recommend the book 'Numerical Recipes: The Art of Scientific Computing, Third Edition (2007)', published by Cambridge University Press'. The code in SRS1 Cubic Spline for Excel is based on the cubic spline in that book.

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### Version Info

#### V2.6 (latest version)

- Enhancements - Several minor fixes and updated system support
- Supported Platforms - This version requires Microsoft Excel 2010 or later. Both 32 bit and 64 bit versions of Excel are supported.

#### V2.51

- Fix - Fixed a problem that sometimes could interfere with copy / paste of data
- Enhancements - Several minor cosmetic enhancements
- Supported Platforms - This version requires Microsoft Excel 2007 or later. Both 32 bit and 64 bit versions of Excel are supported.

#### V2.5

- Works with 64 bit Excel - This new version supports 64 bit versions of Excel and as well as the 32 bit versions. The previous version (2.0) only worked with the 32 bit versions of Excel.
- New Spline Functions - This version adds several new spline functions, includes "BesselSpline" and "OneWaySpline". The BesselSpline is similar to a cubic spline, but can be better behaved with fewer unwanted oscillations between data points. The OneWaySpline is a monotonic spline. If your dataset is only increasing or only decreasing, then the OneWaySpline will produce results that also do not change direction.
- Supported Platforms - This version requires Microsoft Excel 2007 or later. Both 32 bit and 64 bit versions of Excel are supported.

#### V2.0

- Improved performance - This new version is a compiled .net add-in. It calculates faster and is more robust than the previous version, which was based on VBA (Version 1.xx).
- Functions Included - This version includes both a cubic spline function, as well as a linear interpolation function.
- Supported Platforms - This version requires Microsoft Excel 2007 or later. (Note - the download also includes a copy of the older version which supports earlier versions of Microsoft Excel in case you do not have Microsoft Excel 2007 or later.)

#### V1.03

- Supported Platforms - This version works with almost any version of Microsoft Excel (Excel 95 or later)
- Configuration - This version is written in the Visual Basic for Applications language, and the source code is accessible by users