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Preface to First Edition - lib

Preface to First Edition - lib

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146 DENSITY ESTIMATIONR> epa x epavals persp(x = x, y = x, z = epavals, xlab = "x", ylab = "y",+ zlab = expression(K(x, y)), theta = -35, axes = TRUE,+ box = TRUE)K(x, y)yxFigure 8.3 Epanechnikov kernel for a grid between (−1.1, −1.1) and (1.1, 1.1).which is implemented and depicted in Figure 8.3, here by using the perspfunction for plotting in three dimensions.According <strong>to</strong> Venables and Ripley (2002) the bandwidth should be chosen<strong>to</strong> be proportional <strong>to</strong> n −1/5 ; unfortunately the constant of proportionalitydepends on the unknown density. The tricky problem of bandwidth estimationis considered in detail in Silverman (1986).© 2010 by Taylor and Francis Group, LLC

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