Category Archives: Maths

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

Counting non-pecked chicks

Posted on 16/06/2017 by dougaj4

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 →

Posted in Excel, Link to Python, Maths, Newton, UDFs, VBA, xlwings | Tagged , , , , , , , | Leave a comment

More on trend line equations on line charts

Posted on 27/04/2017 by dougaj4

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 , , , , | 1 Comment

Displaying trend line equations on line charts

Posted on 16/04/2017 by dougaj4

This post is prompted by a recent comment at Using LINEST for non-linear curve fitting which found that the trend line formula displayed on a chart was totally different from that found using the Linest function. The problem was caused by using a … Continue reading →

Posted in Charts, Charts, Excel, Maths | Tagged , , , | Leave a comment

Weighted Least Squares Regression, using Excel, VBA, Alglib and Python

Posted on 05/02/2017 by dougaj4

Least squares linear regression in Excel is easy.  That’s what the Linest and Trend functions do.  That is, they find the coefficients of a straight line (or higher dimension shape) so that the sum of the squares of the distances of … Continue reading →

Posted in AlgLib, Curve fitting, Excel, Link to Python, Maths, Newton, NumPy and SciPy, UDFs, VBA | Tagged , , , , , , | 9 Comments