Fagan Nomogram Function — nomogrammer • meddecide

Create the Fagan nomogram for Bayesian analysis in diagnostic testing

Usage

nomogrammer(
  Prevalence,
  Sens = NULL,
  Spec = NULL,
  Plr = NULL,
  Nlr = NULL,
  Detail = FALSE,
  NullLine = FALSE,
  LabelSize = (14/5),
  Verbose = FALSE
)

Arguments

Prevalence: Prior probability / prevalence as a number between 0 and 1
Sens: Model sensitivity as a number between 0 and 1 (optional if Plr/Nlr provided)
Spec: Model specificity as a number between 0 and 1 (optional if Plr/Nlr provided)
Plr: Positive likelihood ratio (calculated from Sens and Spec if not provided)
Nlr: Negative likelihood ratio (calculated from Sens and Spec if not provided)
Detail: If TRUE, will overlay key statistics onto the plot
NullLine: If TRUE, will add a line from prior prob through LR = 1
LabelSize: Tweak this number to change the label sizes
Verbose: Print out relevant metrics in the console

Value

A ggplot object with the Fagan nomogram

Examples

# Using sensitivity and specificity
nomogrammer(Prevalence = 0.3, Sens = 0.9, Spec = 0.8)


# Using likelihood ratios
nomogrammer(Prevalence = 0.3, Plr = 4.5, Nlr = 0.125)