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# Category Archives: Maths

## Using Alglib least-squares solvers

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 AlgLib, Excel, Levenberg Marquardt, lsfit, minlm, Numpy, Python, SciPy, UDF, VBA, xlwings
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## Working with implied units

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 ACI 318, Customary US Units, Eval, EvalU, Evaluate text, Excel, Implied units, shear capacity, SI Units, UDF, Units aware, Units4Excel, VBA
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## Evaluating text and calling Python functions from Excel with xlwings

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 AlgLib, call Python functions, evaluate text strings, Excel, Numpy, Python, SciPy, UDF, VBA, xlwings
1 Comment

## Excel to Alglib via xlwings

The Alglib library provides many valuable numerical analysis routines, but the VBA version is no longer actively maintained.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 AlgLib, Cubic Spline functions, curve fitting, Excel, Higher order polynomials, Matrix Functions, Python, UDF, VBA, xlwings
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## Plotting Freeze-Thaw Data …

… 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 cyclic data, Excel, Freeze-thaw curve, sigmoid curve, UDF, VBA
1 Comment

## Counting non-pecked chicks

Download file: Binary Chicks.zip. This post is based on a recent discussion at Cosmic Horizons looking at numerical methods to solve the following problem: The answer to the question is straightforward: With a little thought, you should be able to realise … Continue reading

## More on trend line equations on line charts

In the previous post we saw that if a trend line equation is added to a line chart it will return the wrong coefficients if the x values are not a continuous sequence of integers, starting at 1 (click on … Continue reading

Posted in Charts, Excel, Maths, Newton
Tagged chart trend line, Charts, Excel, line chart, XY chart
1 Comment