COMS 482: unofficial class blog

Lecture 13: Change Detection in Lines

Posted in Class Notes by Elliott Back on February 21st, 2005.

On change detection in sequences of points. Segmented Least Squares with multi-way choices. Read section 6.3 in the book.

Algorithm:

For all pairs (i, j) | i <= j, compute the least squares error ei, j for the segment pi … pj
C is a constant that defines the range of allowable error

For j = 1 to n
    For i = 1 to j
        OPT(j) = min(ei, j + C + OPT(i-1));
    End For
EndFor

Return OPT(n)

Reasoning:

We partition the set of points into the set of all possible line segments. Then, for each line segment we compute the error of a least-squares fit through that line segment. Then, we iterate through all the line segments, finding the last point which has “acceptable” error, otherwise starting a new subsequence. In this way, we choose an optimal number and location of least squares fits for our data.

This entry was posted on Monday, February 21st, 2005 at 11:20 pm and is tagged with least squares, nbsp nbsp nbsp nbsp nbsp, line segments, line segment, allowable error, acceptable error, optimal number, subsequence, section 6, pj, partition, algorithm, sequences, pairs, pi, lt, choices. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback.

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