Compositional (version 1.1)

fast.alfa: Fast estimation of the value of $\alpha$

Description

Fast estimation of the value of $\alpha$.

Usage

fast.alfa(x, B = 1, ncores = 1)

Arguments

x

A matrix with the compositional data. No zero vaues are allowed.

B

If no (bootstrap based) confidence intervals should be returned this should be 1 and more than 1 otherwise.

ncores

If ncores is greater than 1 parallel computing is performed.

Value

• A vector with the best alpha, the maximised log-likelihood and the log-likelihood at $\alpha=0$, when B = 1 (no bootstrap) or a list including:
• param
  The best alpha and the value of the log-likelihod, along with the 95% bootstrap based confidence intervals if B is greater than 1.
• message
  A message with some information about the histogram if B is greater than 1.

Details

This is a faster function than profile for choosing the value of $\alpha$.

References

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. http://arxiv.org/pdf/1106.1451.pdf

See Also

alfa.profile, alfa, alfainv

Examples

library(MASS)
x <- iris[, 1:4]
fast.alfa(x)
alfa.profile(x)