Debugging functions from Base R or other packages depend on the complexities of those functions, and how the functions call other functions.
Option 1: Use debug
Code
set.seed(1234)
n = 20
y1 = round(rnorm(n, 16, 4), 2)
g1 = rep("1", length = n)
y2 = round(rnorm(n, 20, 4), 2)
g2 = rep("2", length = n)
DF = data.frame(y = c(y1, y2), Group = c(g1, g2), stringsAsFactors = TRUE)
debug(lm)
fm = lm(y ~ Group, data = DF)
undebug(lm)
Option 2: Use trace
Code
set.seed(1234)
n = 20
y1 = round(rnorm(n, 16, 4), 2)
g1 = rep("1", length = n)
y2 = round(rnorm(n, 20, 4), 2)
g2 = rep("2", length = n)
DF = data.frame(y = c(y1, y2), Group = c(g1, g2), stringsAsFactors = TRUE)
trace(lm, tracer = browser, at = 10)
fm = lm(y ~ Group, data = DF)
untrace(lm)
Option 3: Use trace with edit arguments
If the function is a stand-alone funciton, you may create a copy of the function, rename the function and almost evaluate it as your own function.