fit_weibull_plot: Fit and Plot Three-Parameter Weibull Distribution with...

In dendrometry: Forest Estimations and Dendrometric Computations

Fit and Plot Three-Parameter Weibull Distribution with Confidence Bands

Description

Fits a three-parameter Weibull distribution to diameter data and optionally visualizes the fit with a histogram, fitted density curve, and confidence bands.

Usage

fit_weibull_plot(
  x,
  amplitude = 10,
  shape = 2,
  plot = TRUE,
  show_ci = TRUE,
  ci_level = 0.95,
  ci_method = "delta",
  n_boot = 1000,
  main = NULL,
  title.col = "black",
  mid = TRUE,
  line.col = "blue",
  ci.col = "lightblue",
  ci.alpha = 0.3,
  legendPos = "topright",
  lowLim = NULL,
  ymax = NULL,
  bg = "aliceblue",
  method = "mle",
  ties_method = "cheng_amin",
  cex.axis = 0.6,
  cex.lab = 0.8,
  las = 1,
  xlab = "Diameter class (cm)",
  ylab = "Relative frequency (%)",
  cex.legend = 1,
  ...
)

adjWeibull(
  x,
  amplitude = 10,
  shape = 2,
  plot = TRUE,
  show_ci = TRUE,
  ci_level = 0.95,
  ci_method = "delta",
  n_boot = 1000,
  main = NULL,
  title.col = "black",
  mid = TRUE,
  line.col = "blue",
  ci.col = "lightblue",
  ci.alpha = 0.3,
  legendPos = "topright",
  lowLim = NULL,
  ymax = NULL,
  bg = "aliceblue",
  method = "mle",
  ties_method = "cheng_amin",
  cex.axis = 0.6,
  cex.lab = 0.8,
  las = 1,
  xlab = "Diameter class (cm)",
  ylab = "Relative frequency (%)",
  cex.legend = 1,
  ...
)

Arguments

x	numeric vector of diameter observations (typically tree diameters in cm).
amplitude	numeric bin width for histogram (default: 10).
shape	numeric initial value for shape parameter (default: 2).
plot	logical; if TRUE, produces a histogram with fitted curve (default: TRUE).
show_ci	logical; if TRUE, displays confidence bands around fitted curve (default: TRUE). Only applicable when plot = TRUE and standard errors are available.
ci_level	numeric confidence level for bands (default: 0.95).
ci_method	character string for CI computation: "delta" (delta method using vcov), "bootstrap" (parametric bootstrap), or "both" (default: "delta").
n_boot	integer number of bootstrap samples (default: 1000). Only used if ci_method is "bootstrap" or "both".
main	character string for plot title (default: NULL).
title.col	color for legend title (default: "black").
mid	logical; if TRUE, curve is drawn from min to max of bin midpoints; if FALSE, from min to max of bin breaks (default: TRUE).
line.col	color for fitted curve (default: "blue").
ci.col	color for confidence bands (default: "lightblue").
ci.alpha	numeric transparency for confidence bands (default: 0.3).
legendPos	position of legend (default: "topright").
lowLim	numeric lower limit for histogram breaks (default: NULL, uses min(x)).
ymax	numeric upper limit for y-axis (default: NULL, auto-computed).
bg	background color for legend box (default: "aliceblue").
method	character string specifying estimation method. Options: "mle" (Maximum Likelihood - default), "mps" (Maximum Product Spacing), "mom" (Method of Moments).
ties_method	character string for ties correction in MPS: "cheng_amin", "none", or "cheng_stephens" (default: "cheng_amin"). Only used when method = "mps".
cex.axis	numeric character expansion factor for axis annotation (default: 0.6).
cex.lab	numeric character expansion factor for axis labels (default: 0.8).
las	numeric orientation of axis labels (default: 1).
xlab	character string for x-axis label (default: "Diameter class (cm)").
ylab	character string for y-axis label (default: "Relative frequency (%)" ).
cex.legend	numeric character expansion factor for legend (default: 1).
...	additional graphical parameters passed to plot.

Value

A list (invisibly) containing:

estimate	Named vector of parameter estimates (shape, scale, location)
se	Standard errors (NULL if unavailable or method doesn't support it)
vcov	Variance-covariance matrix (NULL if unavailable)
ci	Confidence intervals for parameters at specified level (NULL if unavailable)
measures	Named vector of goodness-of-fit statistics (KS statistic, p-value, AIC, BIC)
convergence	Integer convergence code (0 = successful)
method	Character string of estimation method used
ci_method	Character string of confidence interval method used
ci_level	Numeric confidence level used
note	Character string with interpretation note for KS test

See Also

fit_dist

Examples

# Simulate tree diameter data
set.seed(123)
diameters <- rweibull3(100, shape = 2.5, scale = 25, loc = 10)

# Fit with confidence bands
fit1 <- fit_weibull_plot(diameters, amplitude = 5, show_ci = TRUE)

# Fit without confidence bands
fit2 <- fit_weibull_plot(diameters, amplitude = 5, show_ci = FALSE)

# Use bootstrap confidence bands
fit3 <- fit_weibull_plot(diameters,
  amplitude = 5,
  ci_method = "bootstrap", n_boot = 500
)

dendrometry documentation built on Nov. 5, 2025, 5:23 p.m.