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Thread: detrending data

  1. #1
    4 Star Lounger
    Join Date
    May 2002
    Thanked 0 Times in 0 Posts
    I have a series of aquifer data with a declining trend, as shown on the attached figure. I would like to remove the trend from the data, assuming the trend to be evenly distributed over time. A linear fit gives the following formula: Y = -0.01652018039 * X + 667.9871968.

    And over the time period indicated, the Y value trend decreases 0.13 ft. To make the correction, I divided that value (0.13) by the number of points (1152) and cumulated them where the first cell (C1) was 0.13/1152, the 2nd cell was C1+0.13/1152, the 3rd cell was C2+0.13/1152, etc. I then added the cumulated trend to the original data. It works, but itís not very elegant.

    Is there a better way to do this?


  2. #2
    Plutonium Lounger
    Join Date
    Mar 2002
    Thanked 28 Times in 28 Posts
    I don't see an attachment...

    Why not subtract the linear trend, or at least the -0.01652018039 * X part of it from the Y values?

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