qreference {DAAG} | R Documentation |

## Simulate QQ reference plots

### Description

This function computes the QQ plot for given data and specified distribution, then repeating the comparison for data simulated from the specified distribution. The plots for simulated data give an indication of the range of variation that is to expected, and thus calibrate the eye.

### Usage

```
qreference(test = NULL, m = 30, nrep = 6, pch=c(16,2), distribution = function(x) qnorm(x,
mean = ifelse(is.null(test), 0, mean(test)), sd = ifelse(is.null(test),
1, sd(test))), seed = NULL, nrows = NULL, cex.strip = 0.75,
xlab = NULL, ylab = NULL)
```

### Arguments

`test` |
a vector containing a sample to be tested; if not supplied, all qq-plots are for data simulated from the reference distribution |

`m` |
the sample size for the reference samples; default is test sample size if test sample is supplied |

`nrep` |
the total number of samples, including reference samples and test sample if any |

`pch` |
plot character(s) |

`distribution` |
reference distribution; default is standard normal |

`seed` |
the random number generator seed |

`nrows` |
number of rows in the plot layout |

`cex.strip` |
character expansion factor for labels |

`xlab` |
label for x-axis |

`ylab` |
label for y-axis |

### Value

QQ plots of the sample (if test is non-null) and all reference samples

### Author(s)

J.H. Maindonald

### Examples

```
# qreference(rt(30,4))
# qreference(rt(30,4), distribution=function(x) qt(x, df=4))
# qreference(rexp(30), nrep = 4)
# toycars.lm <- lm(distance ~ angle + factor(car), data = toycars)
# qreference(residuals(toycars.lm), nrep = 9)
```

*DAAG*version 1.25.6 Index]