Estimation of the value of α via the alfa profile log-likelihood
Estimation of the value of α via the alfa profile log-likelihood.
alfa.profile(x, a = seq(-1, 1, by = 0.01))
x |
A matrix with the compositional data. Zero values are not allowed. |
a |
A grid of values of α. |
For every value of α the normal likelihood (see the refernece) is computed. At the end, the plot of the values is constructed.
A list including:
res |
The chosen value of α, the corresponding log-likelihood value and the log-likelihood when α=0. |
ci |
An asympotic 95% confidence interval computed from the log-likelihood ratio test. |
Michail Tsagris
R implementation and documentation: Michail Tsagris mtsagris@uoc.gr and Giorgos Athineou <gioathineou@gmail.com>
Tsagris M.T., Preston S. and Wood A.T.A. (2011). A data-based power transformation for compositional data. In Proceedings of the 4th Compositional Data Analysis Workshop, Girona, Spain. https://arxiv.org/pdf/1106.1451.pdf
x <- as.matrix(iris[, 1:4]) x <- x / rowSums(x) alfa.tune(x) alfa.profile(x)
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