lines.thres2: Add threshold lines to a plot (two-state setting)

Description

The function includes vertical lines for the threshold and confidence interval in a plot created with plot.thres2().

Usage

# S3 method for thres2
lines(x, ci = TRUE, which.boot = c("norm", "perc"),
  col = 1, lty = c(1, 2), lwd = 1, ...)

Value

With a plot.thres2 open, this function adds lines for the required threshold.

Arguments

x

an object of class thres2.

ci

should the confidence interval be plotted? Default, TRUE. No confidence interval will be plotted if x does not contain one (that is, x$CI is NULL).

which.boot

in case x contains confidence intervals calculated by bootstrapping, which one should be printed? The user can choose between "norm" (based on normal distribution) or "perc" (based on percentiles). Default, "norm". This argument is ignored if the confidence intervals were calculated by the delta method.

col

color for the threshold and its corresponding confidence interval. Default, 1.

lty

a 2-dimensional vector containing:

lty[1]: line type for the threshold

lty[2]: line type for the confidence interval

Default, c(1, 2). If length(lty) is not 2, lty will be recycled.

lwd

line width for the threshold and its corresponding confidence interval. Default, 1.

...

further arguments to be passed to abline().

References

Skaltsa K, Jover L, Carrasco JL. (2010). Estimation of the diagnostic threshold accounting for decision costs and sampling uncertainty. Biometrical Journal 52(5):676-697.

Examples

Run this code

n1 <- 100
n2 <- 100
set.seed(1234)
par1.1 <- 0
par1.2 <- 1
par2.1 <- 2
par2.2 <- 1
rho <- 0.2
k1 <- rnorm(n1, par1.1, par1.2) # non-diseased
k2 <- rnorm(n2, par2.1, par2.2) # diseased

thres <- thres2(k1, k2, rho, method="eq", ci.method="d")
plot(thres, col=c(1, 2, 4), lwd=c(2, 2, 1), leg.pos="topright")
thresunequal <- thres2(k1, k2, rho, method="unequal", ci=FALSE)
lines(thresunequal, col=3) # almost the same; no confidence interval

if (FALSE) {
  thresboot <- thres2(k1, k2, rho, method="emp", ci.method="b")
  lines(thresboot, col=5, which.boot="norm")
}