Create a linear flow diagram

flow.R

flow <- function (x, switch=NULL) {
  # `x` is a character vector of items to diagram
  # switch is an optional vector (logical or integer)
  #   specifying if the element of `x` is run (TRUE or 1) or not (FALSE or 0)
  # Usage:
  # > flow(c("Part 1", "Part 2", "...", "Part N"),
  # +      c(TRUE, FALSE, ..., TRUE))
  require(DiagrammeR, quietly=TRUE)
  require(devtools, quietly=TRUE)
  if (packageVersion("devtools") >= "1.12.0") {
    source_gist("https://gist.github.com/benjamin-chan/3d569db12bb223e8b3c4",
                filename="colorPalette.R",
                quiet=TRUE)
  } else {
  source_gist("https://gist.github.com/benjamin-chan/3d569db12bb223e8b3c4",
              quiet=TRUE)
  }
  require(extrafont, quietly=TRUE)
  choose_font(c("Lato", "sans"))
  n <- length(x)
  alpha <- rep(255, n)
  if (!is.null(switch)) {alpha[!switch] <- round(1/4 * 255)}
  nodes <- create_nodes(nodes=letters[1:n],
                        label=x,
                        style="filled",
                        fontcolor="white",
                        fontsize="30pt",
                        color=paste0(colorPalette()[1], sprintf("%x", alpha)),
                        shape="oval")
  edges <- create_edges(from=letters[1:n-1],
                        to  =letters[2:n])
  G <- create_graph(nodes_df=nodes, 
                    edges_df=edges,
                    graph_name="Processing sequence",
                    node_attrs="fontname=\"Lato\"", 
                    graph_attrs=c("layout=dot"))
  render_graph(G)
}