Integration/area under a curve VBA code?

[WayneL]

Hi



I have built a spreadsheet that can calculate the area under a curve of a
set of data but I would like to have this in VBA for Excel, in say
Integral(C1,C2) format or a button on the toolbar.

Can anyone point me in the right direction for acquiring the code?



Cheers



WayneL

 

[WayneL]

Thanks Gregory Vainberg (http://www.vbnumericalmethods.com) for this perfect
solution.

I have tested it with FlexPro and the value correlates.

Cheers

WayneL



Hey Wayne,

I have a number of different methods that you can use, but the easiest
technique is trapezoidal integration. On the website I have a version that
takes the function name as a parameter, but it can be easily adapted to use
2 vectors as parameters as follows:

Public Function TRAPnumint(x, y) As Double

n = Application.Count(x)

TRAPnumint = 0

For t = 2 To n

TRAPnumint = TRAPnumint + 0.5 * (x(t) - x(t - 1)) * (y(t - 1) +
y(t))

Next

End Function

Where x is the column of x values and y is the column of f(x) values.

Hope this helps,

Gregory Vainberg

http://www.vbnumericalmethods.com