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17.7: Comparing different Methods

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    The main difference between Gibbs, EM, and the Greedy algorithm lies in their maximization step after computing their Z matrix. Examples of the Z matrix are graphically represented below.THis Z matrix is then used to recompute the original profile matrix until convergence. Some examples of this matrix are graphically represented by 17.8

    page281image26784352.png
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    Figure 17.8: Examples of the Z matrix computed via EM, Gibbs Sampling, and the Greedy Algorithm

    Intuitively, the greedy algorithm will always pick the most probable location for the motif. The EM algorithm will take an average of all values while Gibbs Sampling will actually use the probability distribution given by Z to sample a motif in a step.

    page281image26782064.png
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    Figure 17.9: Selecting motif location: the greedy algorithm will always pick the most probable location for the motif. The EM algorithm will take an average while Gibbs Sampling will actually use the probability distribution given by Z to sample a motif in each step

    This page titled 17.7: Comparing different Methods is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Manolis Kellis et al. (MIT OpenCourseWare) via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.