# Shade: Produce a Shaded Curve In DescTools: Tools for Descriptive Statistics

## Description

Sometimes the area under a density curve has to be color shaded, for instance to illustrate a p-value or a specific region under the normal curve. This function draws a curve corresponding to a function over the interval `[from, to]`. It can plot also an expression in the variable `xname`, default `x`.

## Usage

 `1` ```Shade(expr, col = par("fg"), breaks, density = 10, n = 101, xname = "x", ...) ```

## Arguments

 `expr` the name of a function, or a `call` or an `expression` written as a function of `x` which will evaluate to an object of the same length as `x`. `col` color to fill or shade the shape with. The default is taken from `par("fg")`. `breaks` numeric, a vector giving the breakpoints between the distinct areas to be shaded differently. Should be finite as there are no plots with infinite limits. `density` the density of the lines as needed in polygon. `n` integer; the number of x values at which to evaluate. Default is 101. `xname` character string giving the name to be used for the x axis. `...` the dots are passed on to `polygon`.

## Details

Useful for shading the area under a curve as often needed for explaining significance tests.

## Value

A list with components `x` and `y` of the points that were drawn is returned invisibly.

## Author(s)

Andri Signorell <andri@signorell.net>

`polygon`, `curve`

## Examples

 ```1 2 3 4 5 6``` ```curve(dt(x, df=5), xlim=c(-6,6), main=paste("Student t-Distribution Probability Density Function, df = ", 5, ")", sep=""), type="n", las=1, ylab="probability", xlab="t") Shade(dt(x, df=5), breaks=c(-6, qt(0.025, df=5), qt(0.975, df=5), 6), col=c(hred, hblue), density=c(20, 7)) ```

### Example output ```
```

DescTools documentation built on June 17, 2021, 5:12 p.m.