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)

Usage

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.

Value

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.

References

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

Examples

beta_parms_from_quantiles(c(0.5,0.99))
#> $a
#> [1] 5.967161
#> 
#> $b
#> [1] 1.261544
#> 
#> $last.change
#> [1] -1.493917e-04 -6.358114e-05
#> 
#> $niter
#> [1] 5
#> 
#> $q
#> [1] 0.50 0.99
#> 
#> $p
#> [1] 0.025 0.975
#> 
#> $p.check
#> [1] 0.025 0.975
#>