LWR: Plot and Model Length-Weight Relationships with Optional Log...

In aLBI: Estimating Length-Based Indicators for Fish Stock

Plot and Model Length-Weight Relationships with Optional Log Transformation

Description

This function visualizes and models the relationship between length and weight (or any two continuous variables) using linear regression. It supports both standard and log-transformed models, producing a ggplot2-based plot with a fitted line, optional confidence interval shading, and annotations for the regression equation, R^2, and p-value. When save_output is TRUE, the plot and model summary are saved to the working directory as a PDF and text file, respectively.

Usage

LWR(
  data,
  log_transform = TRUE,
  point_col = "black",
  line_col = "red",
  shade_col = "red",
  point_size = 2,
  line_size = 1,
  alpha = 0.2,
  main = "Length-Weight Relationship",
  xlab = NULL,
  ylab = NULL,
  save_output = TRUE
)

Arguments

data	A data frame with at least two columns: the first for length, the second for weight.
log_transform	Logical. Whether to apply a log-log transformation to the variables. Default is TRUE.
point_col	Color of the data points. Default is "black".
line_col	Color of the regression line. Default is "red".
shade_col	Color for the confidence interval ribbon. Default is "red".
point_size	Size of the data points. Default is 2.
line_size	Size of the regression line. Default is 1.
alpha	Transparency for the confidence interval ribbon. Default is 0.2.
main	Title of the plot. Default is "Length-Weight Relationship".
xlab	Optional. Custom x-axis label. If NULL, a label is generated based on log_transform.
ylab	Optional. Custom y-axis label. If NULL, a label is generated based on log_transform.
save_output	Logical. Whether to save the plot as a PDF and the model summary as a text file. Default is TRUE.

Value

A list containing:

model	The fitted lm object
intercept	The estimated intercept (back-transformed if log_transform = TRUE)
slope	The estimated slope
r_squared	R-squared value
correlation_r	Correlation coefficient (r)
p_value	P-value for slope
plot	The ggplot object for further customization

Examples

data(LWdata, package = "aLBI")
result <- LWR(LWdata, log_transform = TRUE, save_output = FALSE)
print(result$plot)

aLBI documentation built on Aug. 8, 2025, 6:06 p.m.