How to debug (placing break point,etc) an installed R package in RStudio?

breakpoints, debugging, r, rstudio

Solution

Look at `trace`. Here is an example adding a breakpoint at the fourth statement in the base package function `var`. Here we ask `trace` to invoke the function `browser` at the sixth statement:

> trace(var, browser, at=6)
Tracing function "var" in package "stats"
[1] "var"
> var(1:10)
Tracing var(1:10) step 6 
Called from: eval(expr, envir, enclos)
Browse[1]> n
debug: if (is.data.frame(y)) y <- as.matrix(y) else stopifnot(is.atomic(y))
Browse[2]> n
debug: stopifnot(is.atomic(y))
Browse[2]> n
debug: .Call(C_cov, x, y, na.method, FALSE)
Browse[2]> n
[1] 9.166667

Remember to `untrace` when you're done. You can do fairly complex stuff with `trace`, though in most cases `trace(fun.name, browser)` is probably enough.

Alternatively, you can just load the package and type the name of the function on the command line like so:

> var
function (x, y = NULL, na.rm = FALSE, use) 
{
    if (missing(use)) 
        use <- if (na.rm) 
            "na.or.complete"
        else "everything"
    na.method <- pmatch(use, c("all.obs", "complete.obs", "pairwise.complete.obs", 
        "everything", "na.or.complete"))
    if (is.na(na.method)) 
        stop("invalid 'use' argument")
    if (is.data.frame(x)) 
        x <- as.matrix(x)
    else stopifnot(is.atomic(x))
    if (is.data.frame(y)) 
        y <- as.matrix(y)
    else stopifnot(is.atomic(y))
    .Call(C_cov, x, y, na.method, FALSE)
}
<bytecode: 0x000000000928ad30>
<environment: namespace:stats>

You can then copy that into your editor and play around with it, add your `browser` statement, and step through the results.

Problem

Original source