Fits a broken-stick model to estimate size at maturity. Code
adapted from Dr. Bradley Stevens at the University of Maryland Eastern
Shore. Differs from the broken-stick methods implemented in regrans(),
chngpt::chngpt(), segmented::segmented(), SiZer::piecewise.linear(),
etc. in that only values of the x-axis variable present in the data are
tested as possible SM50 values.
Usage
broken_stick_stevens(
dat,
xvar,
yvar,
lower = NULL,
upper = NULL,
log = FALSE,
verbose = FALSE
)Arguments
- dat
data frame or matrix containing the data
- xvar
Name of column (integer or double) of measurements for the x-axis variable (e.g., carapace width).
- yvar
Name of column (integer or double) of measurements for the y-axis variable (e.g., claw height).
- lower
Integer or double; the lower bound for possible SM50 values. Must be on the same scale of the data. Defaults to the 20th percentile of the x-variable.
- upper
Integer or double; the upper bound for possible SM50 values. Must be on the same scale of the data. Defaults to the 80th percentile of the x-variable.
- log
Boolean; should both variables be log-transformed before performing the regression? Defaults to FALSE.
- verbose
Should additional output be returned besides the SM50 estimate?
Value
If verbose is FALSE (the default), an estimate of SM50. Otherwise, output is a list that also includes the original data with a column representing which line (immature or mature) the point was assigned to, the immature amd mature slope and intercept parameters, and the F and p-values for the final piecewise model.
Examples
set.seed(12)
fc <- fake_crustaceans(n = 100, L50 = 100, allo_params = c(1, 0.2, 1.1, 0.2))
broken_stick_stevens(fc, xvar = "x", yvar = "y", verbose = FALSE)
#> [1] 91.10524