MtreeRing (version 1.1)

nearPith: Calibrate ring-width series

Description

This function can calibrate the ring-width series using arcs of inner rings.

Usage

nearPith(ring.data, inner.arc = TRUE, last.yr = NULL, 
      color = 'black', border.type = 16, label.cex = 1.5)

Arguments

ring.data

A magick image object produced by imgInput.

inner.arc

A logical value indicating whether to calibrate the ring-width series using the arcs of inner rings. See details

last.yr

NULL or an integer giving the year of formation of the left-most ring. If NULL, index numbers (starting from 1) is used instead of the year.

color

Color for labels

border.type

Symbol for ring borders. See pch in points for possible values and their shapes.

label.cex

The magnification to be used for years and ring numbers.

Value

A data frame containing the calibrated ring-width series.

Details

This function allows the user to create a path and visually identify ring borders by clicking on the graphical window generated by imgInput.

• If inner.arc = TRUE, the ring-width series is calibrated using arcs of inner rings (Duncan, 1989).

  First, the user can click the left mouse button to add a horizontal path. The path should traverse an appropriate arc (read the reference below for more details). Then, the user can add three points to the selected arc by left-clicking. The first point should be placed on the left endpoint of the arc and the second point is placed on the right endpoint.

  After adding two points, a vertical dashed line will be plotted automatically according to the (x,y) positions of endpoints. The third points should be placed on the intersection of the vertical dashed line and the selected arc.

  Finally, the user is prompted to visually mark ring borders along the path. The termination of visual selection is similar to visualSelect. Note that the left endpoint of the arc will be considered as the last ring border on the path without the need to mark it.

  The ring-width series are corrected using formulas proposed by Duncan (1989).

• If inner.arc = FALSE, the user can create a path following the direction of pith.

  First, the user can add two points by left-clicking on the image. A path passing through these two points will be plotted. The path should be selected along the rays from bark to pith.

  Then, the user can visually mark ring borders along the path. The termination of visual selection is similar to visualSelect.

References

Duncan R. (1989) An evaluation of errors in tree age estimates based on increment cores in Kahikatea (Dacrycarpus dacrydiodes). New Zealand Natural Sciences 16(4), 1-37.

Examples

# NOT RUN {
## Find the image file name in package MtreeRing:
img.name <- system.file("arc.png", package = "MtreeRing")

## Read and plot the image:
t1 <- imgInput(img = img.name, dpi = 1200)

## Use the arcs of inner rings to calibrate ring-width series:
# }
# NOT RUN {
t2 <- nearPith(ring.data = t1, inner.arc = TRUE, last.yr = 2016) 
# }
# NOT RUN {

## Try another method to measure ring widths:
# }
# NOT RUN {
t3 <- nearPith(ring.data = t1, inner.arc = FALSE, last.yr = 2016) 
# }
# NOT RUN {
# }