R/smash.R

In SimonLarsen/smashr: Smash nested lists into tidy data tables.

#' Smash a nested list into a tidy table.
#'
#' @param x List to smash.
#' @param Name Name for column corresponding to each level.
#' @param max.depth Maximum number of recursive levels to flatten.
#' @return A \code{data.table} object.
#'
#' @importFrom tibble tibble
#' @importFrom tibble as_tibble
#' @importFrom dplyr bind_rows
#' @export
smash <- function(x, col.names=NULL, max.depth=Inf) {
  out <- .smash_internal(x, col.names, 1, max.depth)
  colnames(out) <- make.unique(colnames(out))
  return(out)
}

.smash_internal <- function(x, col.names, depth, max.depth) {
  if(depth >= max.depth || any(sapply(x, class) != "list")) {
    return(as_tibble(x))
  }

  out <- lapply(x, .smash_internal, col.names[-1], depth+1, max.depth)
  row_counts <- sapply(out, nrow)

  out <- bind_rows(out)

  if(!is.null(names(x))) {
    out <- cbind(tibble(rep(names(x), row_counts)), out)

    if(!is.null(col.names)) {
      colnames(out)[1] <- col.names[1]
    } else {
      colnames(out)[1] <- paste0("V", depth)
    }
  }

  return(out)
}