Depth-depth curves and correlation"
In admtools: Estimate and Manipulate Age-Depth Models

Depth-depth curves and correlation

library(admtools)

admtools comes with utilities to deal with depth-depth curves that are used for correlation between sections. See the developer documentation (vignette("admtools_doc")) for all available functionality.

Constructing depth-depth curves

There are two ways to construct depth-depth curves: from coeval tie points or from age-depth models. To construct depth-depth curves from coeval tie points use tp_to_ddc (ddc stands for depth-depth curve).

# simulation data
# entries in vectors are coeval bc simulation time steps were identical
h1 = CarboCATLite_data$height_2_km_offshore_m
h2 = CarboCATLite_data$height_12_km_offshore_m
ddc1 = tp_to_ddc(h1 = h1,
                 h2 = h2,
                 L_unit_1 = "m", # associate length units
                 L_unit_2 = "m",
                 sec_1 = "2 km offshore", # name of correlated sections
                 sec_2 = "12 km offshore")

Alternatively, you can use two age-depth models to construct depth-depth curves via adm_to_ddc. This will construct depth-depth curves for the overlapping time interval.

adm_2km = tp_to_adm(t = CarboCATLite_data$time_myr,
                    h = CarboCATLite_data$height_2_km_offshore_m,
                    L_unit = "m",
                    T_unit = "Myr")

adm_8km = tp_to_adm(t = CarboCATLite_data$time_myr,
                    h = CarboCATLite_data$height_8_km_offshore_m,
                    L_unit = "m",
                    T_unit = "Myr")

ddc2 = adm_to_ddc(adm1 = adm_2km, adm2 = adm_8km)
# assign section names
ddc2 = set_section_names(ddc2, sec_names = c("2 km from shore", "8 km from shore"))

Plotting and summaries

You can quickly plot depth-depth curves using plot:

plot(ddc1,
     type = "l",
     xlab = "",
     ylab = "")
mtext(get_section_names(ddc1)[1], side = 1, line = 3)
mtext(get_section_names(ddc1)[2], side = 2, line = 3)

A quick overview of the contents is provided via summary:

summary(ddc1)

Modification

Length units and section names can be extracted and modified using get_L_units, set_L_units, get_section_names and set_section_names. To reverse the direction of correlation, use flip_ddc:

plot(ddc1, type = "l", xlab = "", ylab = "") # correlation from 2 km offshore to 12 km offshore
mtext(get_section_names(ddc1)[1], side = 1, line = 3)
mtext(get_section_names(ddc1)[2], side = 2, line = 3)
ddc3 = flip_ddc(ddc1)
plot(ddc3, type = "l", xlab = "", ylab = "") # correlates 12 km offshore with 2 km offshore
mtext(get_section_names(ddc3)[1], side = 1, line = 3)
mtext(get_section_names(ddc3)[2], side = 2, line = 3)