Thread: FFT with unevenly sampled data in SAC

Started: 2010-01-13 19:18:39
Last activity: 2010-01-13 19:18:39
Topics: SAC Help
Mac Green
2010-01-13 19:18:39
Hi all,

I am using data collected with labview and saved as text files. I have to
sets of data,
the amplitude data set and a set of time intervals which are not even.

I use readtable to import the data into sac and then write it as a sac file.
If my data
was evenly sampled, I would use delta in the header to give the time
interval. Does anyone
know how I can get the FFT of data whose delta is not constant, it I have a
second file with
time intervals?

Thanks.

  • LeRoy Dorman
    2010-01-13 18:17:38
    This question has no simple answer, and is the subject of current research.
    As a starting point you might look at the following papers:
    I. M. Fodor and P. B. Stark, Multitaper Spectral Estimation for Time
    Series with Gaps,
    IEEE transactions on Signal Processing, Vol 48, No 12 December, 2000
    and
    www.congrex.nl/09c24/S3_Posters/S3_P05_Smith_paper.pdf

    Hope this helps.
    LeRoy Dorman

    LeRoy M. Dorman
    Professor Scripps Institution of Oceanography, MC0220
    University of California, San Diego
    9500 Gilman Drive, La Jolla, CA 92093-0220
    voice: +1 858 534-2406 fax: +1 858 534-6849 inet: ldorman<at>ucsd.edu
    http://www.mpl.ucsd.edu/people/ldorman/index.html

    Physical address:
    436 Ritter Hall
    8635 Charles Kennel Way (formerly Discovery Way)
    La Jolla, CA 92037


    Mac Green wrote:
    Hi all,

    I am using data collected with labview and saved as text files. I have
    to sets of data,
    the amplitude data set and a set of time intervals which are not even.

    I use readtable to import the data into sac and then write it as a sac
    file. If my data
    was evenly sampled, I would use delta in the header to give the time
    interval. Does anyone
    know how I can get the FFT of data whose delta is not constant, it I
    have a second file with
    time intervals?

    Thanks.


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