riceff {VGAM} | R Documentation |
Rice Distribution Family Function
Description
Estimates the two parameters of a Rice distribution by maximum likelihood estimation.
Usage
riceff(lsigma = "loglink", lvee = "loglink", isigma = NULL,
ivee = NULL, nsimEIM = 100, zero = NULL, nowarning = FALSE)
Arguments
nowarning |
Logical. Suppress a warning? Ignored for VGAM 0.9-7 and higher. |
lvee , lsigma |
Link functions for the |
ivee , isigma |
Optional initial values for the parameters.
If convergence failure occurs (this VGAM family function
seems to require good initial values) try using these arguments.
See |
nsimEIM , zero |
See |
Details
The Rician distribution has density function
where ,
,
and
is the
modified Bessel function of the
first kind with order zero.
When
the Rice distribution reduces to a Rayleigh
distribution.
The mean is
(returned as the fitted values) where
.
Simulated Fisher scoring is implemented.
Value
An object of class "vglmff"
(see
vglmff-class
). The object is used by modelling
functions such as vglm
and vgam
.
Note
Convergence problems may occur for data where ;
if so, use
rayleigh
or possibly use an
identity
link.
When is large (greater than 3, say) then the mean is
approximately
and the standard deviation
is approximately
.
Author(s)
T. W. Yee
References
Rice, S. O. (1945). Mathematical Analysis of Random Noise. Bell System Technical Journal, 24, 46–156.
See Also
drice
,
rayleigh
,
besselI
,
simulate.vlm
.
Examples
## Not run: sigma <- exp(1); vee <- exp(2)
rdata <- data.frame(y = rrice(n <- 1000, sigma, vee = vee))
fit <- vglm(y ~ 1, riceff, data = rdata, trace = TRUE, crit = "c")
c(with(rdata, mean(y)), fitted(fit)[1])
coef(fit, matrix = TRUE)
Coef(fit)
summary(fit)
## End(Not run)