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Published byBertram Pierce Phillips Modified over 9 years ago
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Kernels in Pattern Recognition
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A Langur - Baboon Binary Problem http://www.tribuneindia.co m/2006/20060712/himplu s4.jpg … HA HA HA … http://www.sickworld.net/ db4/00381/sickworld.net/ _uimages/baboons.jpg
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Representation of Binary Data
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Concept of Kernels Idea proposed by Aizerman in 1964. Feature … space … dimensionality … transformation such that The dot product exists {i.e. is not infinite} in higher dimension & Data is linearly separable.
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Dot Product The scalar value signifies the amount of projection of a in the direction of b The scalar value also signifies the degree of similarity between a and b Adopted from http://www.netcomuk.co.u k/~jenolive/vect6.html
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A Geometrical Interpretation Mapping Mapping data from low dimension to high dimension. Data is linearly separable in higher dimension. Separable hyperplane defined by a normal or weight vector.
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Cross Product Normal vector or Weight vector i.e. perpendicular to the hyperplane. http://www.netcomuk.co.uk/~je nolive/vect8.html Area covered while moving a to b in counterclockwise direction moves the vector upwards... Like tightening of a screw This vector is perpendicular to the plane in which a and b lie.
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Importance of dot product & kernel == dot product Classification requires computation of dot product between normal of hyperplane and test point. Often, normal is expressed as a linear combination of points in higer dimension. Dot products signify on which side of the hyperplane the test point lies – act of classification Dot product computation expensive and transformation not easy to find, so propose a kernel function, whose scalar value is equivalent to the dot product in higer dimensional plane.
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Geometrical Interpretation of Importance of dot product & kernel == dot product
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How does a kernel look like? A Planner View from Top
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How does a kernel look like? An Isometric View from different Side angles
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The End
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Vapnick proposes Support Vector Machines
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An Apple – Orange Binary Problem http://en.wikipedia.org /wiki/Image:Apples.jp g http://en.wikipedia.org /wiki/Image:Ambersw eet_oranges.jpg
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Representation of Binary Data
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Separable Case
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The Lagrangian Optimize Subject to Differentiate w.r.t w weight vector b the constant alpha Lagrangian parameter
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Non-Separable Case
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The Lagrangian Optimize Subject to Differentiate w.r.t w weight vector b the constant alpha Lagrangian parameter xi another Lagrangian paramer
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Finally … after some mental mathematical harrasment we get: Optimized values of weight vector and b values. And Then Use it to classify new test examples …
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In The End If SVMs can’t help classify… then DITCH them and classify apples and oranges by eating them yourself...
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