beta_parms_from_quantiles function

Pick parameters in the Beta distribution to match the specified range

beta_parms_from_quantiles produces prior Beta parameters for the true positive rates (TPR)

beta_parms_from_quantiles(
  q,
  p = c(0.025, 0.975),
  precision = 0.001,
  derivative.epsilon = 0.001,
  start.with.normal.approx = TRUE,
  start = c(1, 1),
  plot = FALSE
)

Arguments

• q: A vector of lower and upper bounds, in which Beta distribution will have quantiles specified by p. For example, q=c(0.5,0.99)
• p: The lower and upper quantiles of the range one wants to specify.
• precision: Approximation precisions.
• derivative.epsilon: Precision of calculating derivative.
• start.with.normal.approx: Default is TRUE, for normal approximation.
• start: Starting values of beta parameters.
• plot: Default is FALSE to suppress plotting of the beta density, otherwise, set to TRUE.

Returns

A list containing the selected Beta parameters a, and b. Other elements of the list include some details about the computations involved in finding a and b.

Examples

beta_parms_from_quantiles(c(0.5,0.99))

References

http://www.medicine.mcgill.ca/epidemiology/Joseph/PBelisle/BetaParmsFromQuantiles.html