gammaFit  R Documentation 
\gamma
Iteratively computes estimate of \gamma
in a model with E_M(y)=x^T\beta
and
Var_M(y)=\sigma^2x^\gamma
.
gammaFit(X, x, y, maxiter = 100, show.iter = FALSE, tol = 0.001)
X 
matrix of predictors in the linear model for y 
x 
vector of x's for individual units in the assumed specification of 
y 
vector of dependent variables for individual units 
maxiter 
maximum number of iterations allowed 
show.iter 
should values of 
tol 
size of relative difference in 
The function gammaFit
estimates the power \gamma
in a model where the variance
of the errors is proportional to x^\gamma
for some covariate x.
Values of \gamma
are typically in [0,2]. The function calls gamEst
.
A list with the components:
g.hat 
estimate of 
converged 

steps 
number of steps used by the algorithm 
Richard Valliant, Jill A. Dever, Frauke Kreuter
Valliant, R., Dever, J., Kreuter, F. (2018, chap. 3). Practical Tools for Designing and Weighting Survey Samples, 2nd edition. New York: Springer.
gamEst
data(hospital)
x < hospital$x
y < hospital$y
X < cbind(sqrt(x), x)
gammaFit(X = X, x = x, y = y, maxiter=100, tol=0.001)
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