R: Estimate theta of the Negative Binomial by Deviance

theta.md {MASS} | R Documentation

## Estimate theta of the Negative Binomial by Deviance

### Description

Given the estimated mean vector, estimate `theta` of the Negative Binomial Distribution by equating the deviance to the residual degrees of freedom. Analogue of a moment estimator.

### Usage

    theta.md(y, u, dfr, limit = 20, eps = .Machine$double.eps^0.25)

### Arguments

`y` | Vector of observed values from the Negative Binomial.
`u` | Estimated mean vector.
`dfr` | Residual degrees of freedom (assuming `theta` known).
`limit` | Limit on the number of iterations.
`eps` | Tolerance to determine convergence.

### Value

The required estimate of `theta`, as a scalar.

### See Also

`glm.nb`, `theta.ml`, `theta.mm`

### Examples

    ## Not run: theta <- theta.md(y, fitted(fm), dfr = 123)

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