unnest a data.frame in base R

unnest.R

#' Unnest a data.frame with one list column
#' @description Will unnest a data.frame that has one list column such that each element
#' of each list has its own row and all other observations are repeated.
#' @param x data.frame
#' @param col character pointing to the list column
unnest <- function(x, col = "set") {
  
  times <- lengths(x[[col]])
  base_names <- names(x)[!names(x) == col]
  
  out <- as.data.frame(cbind(sapply(base_names, function(n) rep(x[[n]], times = times))))
  
  names(out) <- base_names
  
  out[[col]] <- unlist(x[[col]])
  
  out
}

I created this because of all the churn I've had in my use of tidyr::unnest. Hope it helps someone.