Category Archives: Maths

Using Alglib least-squares solvers

Posted on 23/09/2017 by dougaj4

Following the last post on using the Python version of Alglib from Excel, via xlwings, this post looks in more detail at alternatives for fitting a non-linear function to a set of data, using the Levenberg-Marquardt method.  The spreadsheet with … Continue reading →

Posted in AlgLib, Curve fitting, Excel, Link to Python, Maths, Newton, NumPy and SciPy, UDFs, VBA, xlwings | Tagged , , , , , , , , , , | 2 Comments

Working with implied units

Posted on 19/09/2017 by dougaj4

The Units4Excel spreadsheet provides a number of functions to convert between different units and evaluate functions entered as text on the spreadsheet, taking account of the units of both the inputs and the results.  The latest version can be downloaded from: … Continue reading →

Posted in Concrete, Excel, Maths, Newton, UDFs, VBA | Tagged , , , , , , , , , , , , | 2 Comments

Evaluating text and calling Python functions from Excel with xlwings

Posted on 23/08/2017 by dougaj4

The Alglib spreadsheet presented here includes functions to evaluate formulas entered as text on the spreadsheet, or to call specified Python functions.  I have now added a user defined function (UDF) that will perform either of these operations (xl_CallFuncD), and added … Continue reading →

Posted in AlgLib, Excel, Link to Python, Maths, Newton, NumPy and SciPy, UDFs, VBA, xlwings | Tagged , , , , , , , , , | 1 Comment

Excel to Alglib via xlwings

Posted on 11/08/2017 by dougaj4

The Alglib library provides many valuable numerical analysis routines, but the VBA version is no longer actively maintained.  The latest versions are available in C++, C#, and Python, of which the Python version (in conjunction with xlwings) provides the easiest interface … Continue reading →

Posted in AlgLib, Curve fitting, Excel, Link to Python, Maths, Newton, Numerical integration, UDFs, VBA, xlwings | Tagged , , , , , , , , , | 12 Comments

Plotting Freeze-Thaw Data …

Posted on 21/06/2017 by dougaj4

… or other irregular cyclic data. Another Eng-Tips question asked how to approximate ice area over a freeze-thaw cycle using a function based on a sine or cosine curve.  The screen-shot below shows three alternatives: Using built in Excel functions requires … Continue reading →

Posted in Arrays, Curve fitting, Excel, Maths, Newton, UDFs, VBA | Tagged , , , , , | 1 Comment