po_find: po_find
In konradmayer/trlboku: Tree Ring Lab BOKU - a lab internal R function collection

Estimates pith offset of series by finding the position with minimum RSS to existing regional curve.

po_find(
  rwl,
  rc,
  maxpo = NULL,
  min.overlap = 10,
  nyrs = NULL,
  f = 0.5,
  make.plot = TRUE
)

`rwl`	rwl/data.frame object containing the tree ring series.
`rc`	existing "regional curve" as numeric.
`maxpo`	maximal po until which RSS gets calculated.
`min.overlap`	minimum overlap of the curve with the rc curve for a potential po to be mentioned.
`nyrs`	setting for the `ffcsaps` function used to smooth the series: a number greater than 1, affecting the rigidity of the spline. When `f` is kept constant, a larger `nyrs` produces a more rigid spline. Defaults to `length(y)/2`.
`f`	setting for the `ffcsaps` function used to smooth the series: a number between 0 and 1 giving the frequency response at a wavelength of `nyrs` years. When `nyrs` is kept constant, a smaller `f` produces a more rigid spline: At one extreme, `f = 0` causes the function to return the least-squares straight line fit to the data. At the other extreme, `f = 1` results in the natural spline, i.e. the function outputs `y`. The default value is 0.5.
`make.plot`	a `logical` indicating whether a plot should be drawn.