Configure layout parameters for process map

Question

I'm using processmapR to plot my log (purchases) as a process map with custom positions for nodes. here is my code:

positions <- data.frame(act = c("node1","node2","node 3","node 4","node 5","node 6",
                            "node 7","node 8","node 9","Start", "End"),
                    x = c(1,2,3,4,5,6,7,8,9,0,10),
                    y = c(9,8,7,6,5,4,3,2,1,10,0),
                    stringsAsFactors = F
                    )
graph = process_map(purchases, layout = layout_pm(fixed_positions = positions, 
                                              edge_weight = TRUE, 
                                              edge_cutoff = 0), 
                                              render = FALSE)
map = add_global_graph_attrs(graph,
                         attr = "splines",
                         value = "curved", 
                         attr_type = "graph")
render_graph(map)

when I try to run the code, I am faced with the following error:

Error: node 11, position NA,NA!, expected two doubles