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# Category Archives: Maths

## Hofstadter, Pahud, Bach

The latest ACO concert series features the Swiss flautist Emmanuel Pahud (interview here). The performance included J.S. Bach’s 6 Part Ricercar, from The Musical Offering, which was the inspiration for the final dialogue in Douglas Hofstadter’s Godel, Esher, Bach: Achilles … Continue reading

Posted in Bach, Maths, Newton
Tagged AC0, Bach, Douglas Hofstadter, Emmanuel Pahud, Godel Escher Bach, Ricercar a 6
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## Working with implied units – update

Following comments at Eng-Tips I have added two examples with different procedures for evaluating ACI equations for the flexural tensile strength of concrete here.

Posted in 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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## 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
2 Comments

## 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
3 Comments

## 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