View Full Version : area under curve summary

Charles Gatt
12-02-1998, 01:40 PM
Thanks to all who replied about determining area under the
curve with excel data. Here is a summary of responses.

Charlie Gatt

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Consult the following addresses:

software: Mathcad 8


Wolfram Research
software: Mathematica

Best Regards,

Wagner de Godoy
Gait Laboratory
AACD - Brazil
A couple of my PhD students have been using Kaleidagraph with success.


Liz Tanner

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Professor K.E. Tanner
Professor of Biomedical Materials
IRC in Biomedical Materials and Department of Materials
Queen Mary and Westfield College
Mile End Road
E1 4NS

phone +44-171-975-5318
fax +44-181-983-1799
e-mail K.E.Tanner@qmw.ac.uk
I suppose, that you have a certain number of points (lets say n pairs
(x_i,y_i)) which define your curve. The integral is then defined as

I = sum( (y_(i+1) + y_i )/2 * ( x_(i+1) - x_i )

where the sum runs over all points i=1,...,n-1. You should be able to
define this in Excel yourself.



__________________________________________________ _________________________
Dr. Martin Pohl
Department of Orthopaedic Research and Biomechanics
Helmholtzstr. 14
89081 ULM
Germany, EU
phone: +49-(0)731-50-23494 FAX: +49-(0)731-50-23498
WWW: http://pollux.medizin.uni-ulm.de e-mail:
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There is a software which you can download free
it is called accuROC.

Chaim Singal
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Easy, have you got student edition of MATLAB. If so use Trapz function.
Import x,y series as cols. into matlab using LOAD function.
N.B. You dont even have to import x series, as long as you know the
difference between x1,x2 (and it is constant, like time) etc then multiply
the output of Trapz function by (x2-x1). Do it for each series.

One problem though, make sure all col. are of sam length as MATLAB imports
as a matrix (access each col. of matrix in turn). Solution, replace empty
cells with zeros.

Simple, I hope. Any questions I had to do this recently. Takes only a few

William Higgs
Mechanical Engineering
University of Sydney
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Just look in any introductory calculus textbook for calculations of
areas under curves. You could use the trapezoidal approximation,
Simpson's rule or any other approach. You just calculate the formula
for two or three cells and copy it down the column. Dead easy.

Best regards,

J. Michael Lee, Ph.D.
Interim Director, Biomedical Engineering Programme

Associate Professor of Biomaterials (902) 494-6734 (Voice)
Chair, Dept. of Applied Oral Sciences (902) 494-2527 (FAX)
Dalhousie University
5981 University Avenue jmlee@is.dal.ca
Halifax, Nova Scotia (902) 494-2162 Tissue Mechanics Lab
Canada B3H 3J5 (902) 494-6784 Tissue Structure Lab
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BioProc - Software for processing of analog data (contributed by Gordon ERobertson) reads and displays Kistler, APAS and other file formats.
Includes algorithms for smoothing and ensemble averaging of signals.

This program is designed to perform many types of processing on data or
various data or properly formatted ASCII files. There are many different
ways of integrating in this program, and choosing the most appropriate
depends on the type of data being used.

You can download this software from the ISB website. Also, you can download
the Bioproc manual. Follow the instructions for installation from the ISB
website. Lastly, you most likely will have to convert your ascii files into
*.bpa format which will enable Bioproc to read and process you files. This
is freeware software so you can't go wrong. I use this software for
processing GRF forces, EMG data and any sort of other data. It is quite a
powerful tool in your software arsenal.

Dan Ramsey

Motor Control Laboratory Tel: +46 (8)-517-77-503
Astrid Lindgren Hospital Fax: +46 (8)-517-77-351
Karolinska Institute E-mail: Dan.Ramsey@kbh.ki.se
S-171 76 Stockholm

Motorlab Homepage: http://ikaros.f1.ki.se/motorlab/index.htm

Faculty Homepage:
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You can write your own macro to estimate area using something like a
trapezoidal estimation. Here is the code I use in C (you can adapt it as
you like).

/* trapezoidal approximation */
float t=0;
Fs=input("Enter the Frame rate, OR enter -1 if you prefer to
interval time: ");
if(Fs==-1) {
t=input("Enter interval time: "); }
else {
printf("\nInterval time is %1.5f",t); }
for(i=0; i