mom_gamma function

Method of moments for gamma distribution

Compute the shape and scale (or rate) parameters of the gamma distribution using method of moments for the random variable of interest.

mom_gamma(mean, sd, scale = TRUE)

Arguments

• mean: Mean of the random variable.
• sd: Standard deviation of the random variable.
• scale: Logical. If TRUE (default), then the scale parameter is returned; otherwise, the rate parameter is returned.

Returns

If scale = TRUE, then a list containing the parameters shape and scale; otherwise, if scale = FALSE, then a list containing the parameters shape and rate.

Details

If $\mu$ is the mean and $\sigma$ is the standard deviation of the random variable, then the method of moments estimates of the parameters shape = $\alpha > 0$ and scale = $\theta > 0$ are:

and

The inverse of the scale parameter, $\beta = 1/\theta$, is the rate parameter.

Examples

mom_gamma(mean = 10000, sd = 2000)
# The function is vectorized.
mom_gamma(mean = c(8000, 10000), sd = c(1500, 2000))