qntR {DPQ} | R Documentation |

## Pure R Implementation of R's qt() / qnt()

### Description

A pure **R** implementation of R's C API (‘Mathlib’ specifically)
`qnt()`

function which computes (non-central) t quantiles.

The simple inversion (of `pnt()`

) scheme has seen to be deficient,
even in cases where `pnt()`

, i.e., **R**'s `pt(.., ncp=*)`

does not loose accuracy.

### Usage

```
qntR1(p, df, ncp, lower.tail = TRUE, log.p = FALSE,
pnt = stats::pt, accu = 1e-13, eps = 1e-11)
qntR (p, df, ncp, lower.tail = TRUE, log.p = FALSE,
pnt = stats::pt, accu = 1e-13, eps = 1e-11)
```

### Arguments

`p` , `df` , `ncp` |
vectors of probabilities, degrees of freedom, and
non-centrality parameter; see |

`lower.tail` , `log.p` |
logical; see |

`pnt` |
a |

`accu` |
a non-negative number, the “accu”racy desired in the "root finding" loop. |

`eps` |
a non-negative number, used for determining the start interval for the root finding. |

### Value

numeric vector of t quantiles, properly recycled in `(p, df, ncp)`

.

### Author(s)

Martin Maechler

### See Also

Our `qtU()`

and `qtAppr()`

; non-central density and probability
approximations in `dntJKBf`

, and e.g., `pntR`

.
Further, **R**'s `qt`

.

### Examples

```
## example where qt() and qntR() "fail" {warnings; --> Inf}
lp <- seq(-30, -24, by=1/4)
summary(p <- exp(lp))
(qp <- qntR( p, df=35, ncp=-7, lower.tail=FALSE))
qp2 <- qntR(lp, df=35, ncp=-7, lower.tail = FALSE, log.p=TRUE)
all.equal(qp, qp2)## same warnings, same values
```

*DPQ*version 0.5-8 Index]