Category Archives: UDFs

Calling a function as a variable – another example

Posted on 22/04/2010 by dougaj4

The recent posts on the Inverse Quadratic Method and Brent’s Method, and on calling a function as a variable, are leading towards a user defined function (UDF) to analyse circular reinforced concrete sections under combined bending and axial load, but since … Continue reading →

Posted in Concrete, Excel, Maths, UDFs, VBA | Tagged , , , , , | 3 Comments

Digitising logarithmic scales

Posted on 16/04/2010 by dougaj4

At the suggestion of the Exceltipsmonster, I have modified the DigitGraph spreadsheet presented in the previous post to also work with logarithmic scales. Dowload the updated spreadsheet from here. The function now has two additional optional arguments, Xlog and Ylog:  =DigitGraph(Shape Name, … Continue reading →

Posted in Excel, UDFs, VBA | Tagged , , , , | 4 Comments

How to digitise a scanned image

Posted on 14/04/2010 by dougaj4

For instance, suppose we had a graph from a technical paper, and we wanted to extract numerical data from the graph lines.  One way would be to measure the points by hand and calculate the numbers by scaling from the … Continue reading →

Posted in Drawing, Excel, UDFs, VBA | Tagged , , , | 19 Comments

The Inverse Quadratic Method 3 – Brent’s Method

Posted on 13/04/2010 by dougaj4

The previous post in this series presented iterative methods to solve polynomial equations using direct or inverse quadratic interpolation.  These methods have two disadvantages: In some circumstances the function may converge very slowly, or not at all. The name of … Continue reading →

Posted in Excel, Maths, UDFs, VBA | Tagged , , , , , | 12 Comments

Calling a function as a variable

Posted on 08/04/2010 by dougaj4

The functions described in recent posts provide iterative solutions to polynomial equations, but the same method can be used for any equations that can be evaluated numerically and have a single variable.  The question then is, how can we call a … Continue reading →

Posted in Arrays, Excel, Maths, UDFs, VBA | Tagged , , , , , , | 6 Comments