choosePositions {Bchron} | R Documentation |

## Compute positions to date next which result in maximal decrease of chronological uncertainty

### Description

This function finds, for a given current chronology, created via
`Bchronology`

, which positions (depths) to date next
If N = 1 it just finds the position with the biggest uncertainty
If N>1 it puts a date at the N = 1 position and re-runs
`Bchronology`

with the extra psuedo date. It uses the
`unCalibrate`

function with the un-calibrated age estimated
at the median of the chronology and the sd as specified via the
`newSds`

argument. Other arguments specify the new thicknesses,
calibration curves, and outlier probabilities for newly inserted psuedo-dates.

### Usage

```
choosePositions(
bchrRun,
N = 1,
newSds = 30,
newThicknesses = 0,
positions = bchrRun$predictPositions,
newCalCurve = "intcal20",
newOutlierProb = 0.05,
level = 0.5,
plot = TRUE,
count = 1,
linesAt = NULL
)
```

### Arguments

`bchrRun` |
A run of the current chronology as output from |

`N` |
The number of new positions required |

`newSds` |
The new standard deviations of the psuedo-added dates |

`newThicknesses` |
The new thicknesses of the psuedo-added dates |

`positions` |
The positions allowed to estimate the new positions to date. Defaults to the value of |

`newCalCurve` |
The new calibration curve of the psuedo-added dates |

`newOutlierProb` |
The new outlier probabilities of the psuedo-added dates |

`level` |
The confidence level required for minimising the uncertainty. Defaults to 50%. (Note: this will be estimated more robustly than the 95% level) |

`plot` |
Whether to plot the chronologies as they are produced |

`count` |
Counter function (not for use other than by the function itself) |

`linesAt` |
Horizontal line positions (not for use other than by the function itself) |

### Value

Some plots and the positions to date next

### See Also

`Bchronology`

for the main function to create chronologies, `unCalibrate`

for the ability to invert calendar dates for a given calibration curve.

### Examples

```
data(Glendalough)
GlenOut <- Bchronology(
ages = Glendalough$ages,
ageSds = Glendalough$ageSds,
calCurves = Glendalough$calCurves,
positions = Glendalough$position,
positionThicknesses = Glendalough$thickness,
ids = Glendalough$id,
predictPositions = seq(0, 1500, by = 10)
)
# Find out which two positions (depths) to date if we have room for two more dates
# Here going to choose 3 new positions to date
newPositions <- choosePositions(GlenOut, N = 3)
print(newPositions)
# Suppose you are only interested in dating the new depths at 500, 600, or 700 cm
newPositions2 <- choosePositions(GlenOut,
N = 2,
positions = seq(500, 700, by = 10)
)
print(newPositions2)
```

*Bchron*version 4.7.6 Index]