A1inv: Inverse of A1
In circular: Circular Statistics

Description Usage Arguments Details Value Author(s) References See Also Examples

Inverse function of the ratio of the first and zeroth order Bessel functions of the first kind. This function is used to compute the maximum likelihood estimate of the concentration parameter of a von Mises distribution.

A1inv(x)

`x`	numeric value in the interval between 0 and 1.

A1inv(0) = 0 and A1inv(1) = Inf. This function is useful in estimating the concentration parameter of data from a von Mises distribution. Our function use the results in Best and Fisher (1981). Tables use tabulated values by Gumbel, Greenwood and Durand (1953).

Returns the value k, such that A1inv(x) = k, i.e. A1(k) = x.

Claudio Agostinelli

BEST, D.J. and FISHER, N.I. 1981. The bias of the maximum likelihood estimators for the von Mises-Fisher concentration parameters. Communications in Statistics, 10, 493-502.

GUMBEL, E.J., GREENWOOD, J.A. AND DURAND, D. 1953. The circular normal distribution: theory and tables. J. Amer. Statis. Assoc., 48, 131-152.

mle.vonmises, A1, besselI.

#Generate data from a von Mises distribution
data <- rvonmises(n=50, mu=circular(pi), kappa=4)
#Estimate the concentration parameter
s <- sum(sin(data))
c <- sum(cos(data))
mean.dir <- atan2(s, c)
kappa <- A1inv(mean(cos(data - mean.dir)))