chron: Age-depth computation
In paleoMAS: Paleoecological Analysis

Description Usage Arguments Details Value Author(s) See Also Examples

This function computes and returns interpolated ages for specified sample depths based on a matrix with depths and calibrated ages.

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chron(age, depths, max.depth, type = "l", linear = TRUE,
     method = "fmm", ci = TRUE, dates = "points" , length = 0.05,
     digits = 2)

`age`	A numeric matrix with three columns: depths of dated intervals, calibrated ages and standard deviation. The date or suspected date of the uppermost sample MUST be provided (usually 0 cm are present).
`depths`	A vector with a list of depths for which ages will be interpolated. The depths MUST be in ascendant order. Repeated depths are not allowed (see details).
`max.depth`	Maximum depth of the stratigraphic sequence (including analyzed and dated depths). It is used to extrapolate ages when the bottom of the sequence goes beyond the deepest dated interval.
`type`	Graphic parameter for the output plot. See `plot` for details.
`linear`	Interpolation method desired. If TRUE, ages are calculated using linear interpolation. If FALSE, a spline is fitted to the dataset.
`method`	Argument of the function `spline`. This must be one of `"fmm"`, `"natural"`, `"periodic"` or `"monoH.FC"`. Only relevant if `linear=FALSE`. See spline for details.
`ci`	A logical value indicating whether confidence intervals are desired in the output plot.
`dates`	Graphical argument. `"points"` to display dates as red points, or `"bars"` to display dates as error bars spanning the provided standard deviation of calibrated ages.
`length`	Graphical parameter. Length in inches for the horizontal bar heads.
`digits`	Number of digits desired for interpolated ages.

chron calculates interpolated ages using linear interpolation or spline as method. It is based on a three-column matrix with depth of dated interval, calibrated age, and calibrated standard deviation. The interpolated ages are calculated for a set of depths (defined by the user in depths). Whenever the stratigraphic sequence goes beyond the last dated point, the age for the bottom samples is extrapolated. max.depth is the maximum depth of the stratigraphic sequence, including dates and sampled points.

Confidence intervals correspond to the provided chronology deviation. Therefore, it does not necessarily correspond to 0.95 interval.

If there is need to repeat a depth (e.g the floor and roof of a hiatus), the two numbers must be differentiated by at least decimal positions.

A list containing:

`base`	A matrix with the initial chronology.
`chronology`	A matrix with interpolated ages up to `max depth` and with deviation if `ci=TRUE`. The deviation is calculated according to the error provided by the user, therefore it does not necessarily correspond to 0.95 intervals.

Alexander Correa-Metrio, Dunia H. Urrego.

See plot for details on graphic parameters, approx for details on linear interpolation, and spline for details on non-linear interpolation.

data(quexilchron,quexildepths)
#linear interpolation
chron(quexilchron,quexildepths,max.depth=1957,dates="points")
# Spline estimation
chron(quexilchron,quexildepths,max.depth=1957,dates="points")