claude-code-r-skills: Skill for Claude Code

Core Packages

library(brms)
library(cmdstanr)
library(dagitty)
library(ggdag)
library(marginaleffects)
library(tidybayes)
library(bayesplot)

Directed Acyclic Graphs (DAGs)

Prior to causal inference, create and validate DAGs with dagitty and ggdag.

Define DAG Structure

dag <- dagitty('
dag {
  # Node positions for visualization
  exposure [pos="0,1"]
  mediator [pos="1,1"]
  outcome [pos="2,1"]
  confounder [pos="1,0"]

  # Edges (arrows)
  confounder -> exposure
  confounder -> outcome
  exposure -> mediator
  mediator -> outcome
  exposure -> outcome
}
')

Identify Adjustment Sets

# For direct effect
adjustmentSets(dag, exposure = "treatment", outcome = "outcome", effect = "direct")

# For total effect
adjustmentSets(dag, exposure = "treatment", outcome = "outcome", effect = "total")

Validate DAG Against Data

# Get implied conditional independencies
implied_cis <- impliedConditionalIndependencies(dag)

# Test against data
ci_results <- localTests(dag, data = analysis_data, type = "cis")

# Assess validation
ci_df <- as.data.frame(ci_results)
ci_df$independent <- ci_df$p.value > 0.05
pct_supported <- 100 * mean(ci_df$independent, na.rm = TRUE)

cat(sprintf("DAG support: %.1f%% of implied CIs hold\n", pct_supported))

Visualize DAG

dag_tidy <- tidy_dagitty(dag)

ggplot(dag_tidy, aes(x = x, y = y, xend = xend, yend = yend)) +
  geom_dag_edges(edge_colour = "grey50") +
  geom_dag_point(size = 20) +
  geom_dag_text(size = 3.5, color = "black") +
  theme_dag() +
  labs(title = "Causal DAG")

Bayesian Regression with brms

Standard Configuration

options(mc.cores = 4)

# Standard brms model call
model <- brm(
  formula = outcome ~ predictor1 + predictor2 + (1 | group_id),
  data = model_data,
  family = bernoulli(link = "logit"),  # For binary outcomes
  prior = priors,
  sample_prior = "yes",  # For prior-posterior comparison
  chains = 4,
  cores = 4,
  iter = 4000,
  warmup = 1000,
  control = list(
    adapt_delta = 0.95,
    max_treedepth = 15
  ),
  seed = 123,  # Set seed for reproducibility
  backend = "cmdstanr",
  file = "models/model_name",         # Cache compiled model
  file_refit = "on_change"            # Only refit if formula/data change
)