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smoothSurv (version 2.6)

extreme value: Density of the Extreme Value Distribution of a Minimum.

Description

Density function of the extreme value distribution of a minimum with location \(\alpha\) and scale \(\beta\) and the density of the standardized version (with zero mean and unit variance).

Usage

dextreme(x, alpha=0, beta=1)
dstextreme(x)

Value

The value of the density.

Arguments

x

Vector of quantiles.

alpha

Vector of location parameters.

beta

Vector of scale parameters.

Author

Arnošt Komárek arnost.komarek@mff.cuni.cz

Details

Extreme value distribution of a minimum with the location \(\alpha\) and the scale \(\beta\) has a density $$f(x) = \frac{1}{\beta}\exp\left[\frac{x-\alpha}{\beta}-\exp\left(\frac{x-\alpha}{\beta}\right)\right]$$ the mean equal to \(\alpha - \beta\;e\), where \(e\) is approximately \(0.5772\) and the variance equal to \(\beta^2\frac{\pi}{6}\). Its standardized version is obtained with \(\alpha = \frac{\sqrt{6}}{\pi}\;e\) and \(\beta = \frac{\sqrt{6}}{\pi}\)

Examples

Run this code
dextreme(1, (sqrt(6)/pi)*0.5772, sqrt(6)/pi)
dstextreme(1)        ## approximately same result as on the previous row

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