Eric Weeks - personal pages - software

Autocorrelation software

C language source code for calculating the autocorrelation function
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For a brief description of what an autocorrelation function is, click here. Note that my program is not the most efficient way to compute autocorrelations; the best way involves FFT's.

Click here to download software. To compile, use "cc -o autocor autocor.c -lm".

To use the software, you can either specify the filename or pipe the data into the program:

cat datafile | autocor > datafile.mi


autocor datafile > datafile.mi

There are three options. -h lists all the options with a brief comment to remind you what they do. -d (number) sets the maximum delay to calculate the autocorrelation for; the default is 100. This is delay in samples, independent of the other option, which is -t. -t (number) lets you set a time step so that the output is listed in (time lag, autocorrelation) rather than (sample lag, autocorrelation).

Thus, to generate the graph below, I typed:

cat exptcha.dat | autocor -t 0.1 -d 1000 >

If you have questions, please send me email (email address below).

The graph was made with a program I wrote, psdraw. This program is public domain. The program makes PostScript output which I then converted to GIF.

Some links...

Current address:
Eric R. Weeks
Department of Physics
Emory University
Atlanta, GA 30322-2430