rms (version 5.1-3.1)

# ExProb: Function Generator For Exceedance Probabilities

## Description

For an `orm` object generates a function for computing the estimates of the function Prob(Y>=y) given one or more values of the linear predictor using the reference (median) intercept. This function can optionally be evaluated at only a set of user-specified `y` values, otherwise a right-step function is returned. There is a plot method for plotting the step functions, and if more than one linear predictor was evaluated multiple step functions are drawn. `ExProb` is especially useful for `nomogram`.

## Usage

```ExProb(object, …)# S3 method for orm
ExProb(object, codes = FALSE, ...)# S3 method for ExProb
plot(x, …, data=NULL,
xlim=NULL, xlab=x\$yname, ylab=expression(Prob(Y>=y)),
col=par('col'), col.vert='gray85', pch=20,
pch.data=21, lwd=par('lwd'), lwd.data=lwd,
lty.data=2, key=TRUE)```

## Arguments

object

a fit object from `orm`

codes

if `TRUE`, `ExProb` use the integer codes \(1,2,\ldots,k\) for the \(k\)-level response instead of its original unique values

ignored for `ExProb`. Passed to `plot` for `plot.ExProb`

data

Specify `data` if you want to add stratified empirical probabilities to the graph. If `data` is a numeric vector, it is assumed that no groups are present. Otherwise `data` must be a list or data frame where the first variable is the grouping variable (corresponding to what made the linear predictor vary) and the second variable is the data vector for the `y` variable. The rows of data should be sorted to be in order of the linear predictor argument.

x

an object created by running the function created by `ExProb`

xlim

limits for x-axis; default is range of observed `y`

xlab

x-axis label

ylab

y-axis label

col

color for horizontal lines and points

col.vert

color for vertical discontinuities

pch

plotting symbol for predicted curves

lwd

line width for predicted curves

pch.data,lwd.data,lty.data

plotting parameters for data

key

set to `FALSE` to suppress key in plot if `data` is given

## Value

`ExProb` returns an R function. Running the function returns an object of class `"ExProb"`.

`orm`, `Quantile.orm`

## Examples

```# NOT RUN {
set.seed(1)
x1 <- runif(200)
yvar <- x1 + runif(200)
f <- orm(yvar ~ x1)
d <- ExProb(f)
lp <- predict(f, newdata=data.frame(x1=c(.2,.8)))
w <- d(lp)
s1 <- abs(x1 - .2) < .1
s2 <- abs(x1 - .8) < .1
plot(w, data=data.frame(x1=c(rep(.2, sum(s1)), rep(.8, sum(s2))),
yvar=c(yvar[s1], yvar[s2])))

qu <- Quantile(f)
abline(h=c(.1,.5), col='gray80')
abline(v=qu(.5, lp), col='gray80')
abline(v=qu(.9, lp), col='green')
# }
```