边缘的权重属性在"DiagrammeR"R 包上不起作用

Question

我正在尝试使用 R 中的DiagrammeR包向 GraphViz 图添加一些边缘属性。特别是，我想添加属性arrowhead和weight，但只有前者添加到图形中，而不是后者。下面的示例不是真实的示例，而是为了可重复性和清晰度而对其进行的超简化版本。

library(tidyverse)
library(DiagrammeR)
# create nodes
nd <- tibble(
label =  c("A", "B", "C", "D"), 
rank  =  c("1", "0", "2", "2")
)
node <- create_node_df(
n     = nrow(nd),
label = nd$label,
id    =  c(1:nrow(nd)),
# rank  = nd$rank
)
# create edges
ed <- tribble(
~from, ~to, ~arrowhead, ~weight,
1,     2,   'normal',       "5",
1,     3,   'normal',       "1",
3,     4,   'normal',       "1",
3,     2,   'normal',       "1"
)
edge <- create_edge_df(
from      = ed$from,
to        = ed$to,
arrowhead = ed$arrowhead,
weight    = ed$weight
)

# create graph
graph <-
create_graph(
nodes_df   = node,
edges_df   = edge) %>%
add_global_graph_attrs(
attr       = "overlap",
value      = "false",
attr_type  = "graph") %>%
add_global_graph_attrs(
attr       = "layout",
value      = "dot",
attr_type  = "graph")

然而，当我生成dot代码时，weight属性不是边缘的一部分，而是arrowhead

。

graph %>%
generate_dot() %>%
cat()
#> digraph {
#> 
#> graph [layout = 'dot',
#>        outputorder = 'edgesfirst',
#>        bgcolor = 'white',
#>        overlap = 'false']
#> 
#> node [fontname = 'Helvetica',
#>       fontsize = '10',
#>       shape = 'circle',
#>       fixedsize = 'true',
#>       width = '0.5',
#>       style = 'filled',
#>       fillcolor = 'aliceblue',
#>       color = 'gray70',
#>       fontcolor = 'gray50']
#> 
#> edge [fontname = 'Helvetica',
#>      fontsize = '8',
#>      len = '1.5',
#>      color = 'gray80',
#>      arrowsize = '0.5']
#> 
#>   '1' [label = 'A'] 
#>   '2' [label = 'B'] 
#>   '3' [label = 'C'] 
#>   '4' [label = 'D'] 
#> '1'->'2' [arrowhead = 'normal'] 
#> '1'->'3' [arrowhead = 'normal'] 
#> '3'->'4' [arrowhead = 'normal'] 
#> '3'->'2' [arrowhead = 'normal'] 
#> }

我还尝试使用set_edge_attrs()添加属性，但它仍然不起作用。

graph <- graph %>% 
set_edge_attrs(edge_attr = "weight", 
values = "5", 
from = 1, 
to = 2
)
# digraph {
#   
#   graph ...
#  {trimmed output}
#
#   '1'->'2' [arrowhead = 'normal'] 
#   '1'->'3' [arrowhead = 'normal'] 
#   '3'->'4' [arrowhead = 'normal'] 
#   '3'->'2' [arrowhead = 'normal'] 
# }

最后，我不得不手动修改dot代码(见下文(，但鉴于我必须从数据框中的信息生成多个图表，这并不理想。

graph2 <- "digraph {
graph [layout = 'dot',
outputorder = 'edgesfirst',
bgcolor = 'white',
overlap = 'false']
node [fontname = 'Helvetica',
fontsize = '10',
shape = 'circle',
fixedsize = 'true',
width = '0.5',
style = 'filled',
fillcolor = 'aliceblue',
color = 'gray70',
fontcolor = 'gray50']
edge [fontname = 'Helvetica',
fontsize = '8',
len = '1.5',
color = 'gray80',
arrowsize = '0.5']
'1' [label = 'A'] 
'2' [label = 'B'] 
'3' [label = 'C'] 
'4' [label = 'D'] 
'1'->'2' [arrowhead = 'normal', weight = 5] 
'1'->'3' [arrowhead = 'normal', weight = 0] 
'3'->'4' [arrowhead = 'normal', weight = 0] 
'3'->'2' [arrowhead = 'normal', weight = 0]  
}
"
grViz(graph2)

我非常感谢任何帮助。

谢谢。 最好

Answer 1

我不确定这是一个错误还是故意忽略了"权重"，但无论如何，罪魁祸首是DiagrammeR中的一个辅助函数，它生成允许属性的向量generate_dot()并且只允许来自该向量的属性。

# DiagrammeR/R/utils.R
gv_edge_attributes <- function() {
c("style", "penwidth", "color", "arrowsize",
"arrowhead", "arrowtail",
"fontname", "fontsize", "fontcolor",
"len", "tooltip", "URL",
"label", "labelfontname", "labelfontsize",
"labelfontcolor", "labeltooltip", "labelURL",
"edgetooltip", "edgeURL",
"headtooltip", "headURL",
"headclip", "headlabel", "headport",
"tailtooltip", "tailURL",
"tailclip",  "taillabel", "tailport",
"dir", "decorate")
}

如果将"权重"添加到该列表中 - 或修改generate_dot以允许所有属性而不进行检查 - 您的示例工作正常。