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[英]How to choose root node in "dot" graph layout for plotting with networkx and pydot/pygraphviz
[英]"KeyError: Node not in graph" when using pygraphviz_layout even though node is in networkx graph
我有一個由邊緣列表組成的 DataFrame network_df
G = nx.from_pandas_edgelist(network_df,source='Parent Node',target= 'Child Node',create_using=nx.DiGraph())
我正在使用pygraphviz_layout
來計算G
中每個節點的位置
pos = pygraphviz_layout(G,prog="dot", args='-Gnodesep=10-Goverlap=false')
但這會引發以下錯誤:
Exception has occurred: KeyError
Traceback (most recent call last):
File "C:\..\Python37\lib\site-packages\pygraphviz\agraph.py", line 1615, in __new__
nh = gv.agnode(graph.handle, n.encode(graph.encoding), _Action.find)
KeyError: 'agnode: no key'
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "<string>", line 1, in <module>
File "C:\...\Python37\lib\site-packages\networkx\drawing\nx_agraph.py",
line 293, in pygraphviz_layout
node = pygraphviz.Node(A, n)
File "C:\...\Python37\lib\site-
packages\pygraphviz\agraph.py", line 1617, in __new__
raise KeyError("Node %s not in graph." % n)
KeyError: "Node ('', '', 'A /// Standard', 'Event A') not in graph."
但是當我這樣做時
key = ('', '', 'A /// Standard', 'Event A')
print(key in G.nodes())
這打印True
意味着該節點確實在圖中,我在這里做錯了什么?
另外,如果我使用其他一些函數來計算位置,它會起作用
pos = nx.spring_layout(G)
這里有什么問題? pygraphviz_layout
之前在其他數據集上沒有任何問題。
以下應該工作:
import networkx as nx
# an example graph with string (names) as nodes
g = nx.les_miserables_graph()
labels_to_int = {}
int_to_labels = {}
for i, label in enumerate(g):
labels_to_int[label] = i
int_to_labels[i] = label
# update labels to ints with
nx.relabel_nodes(g, labels_to_int, copy=False)
print(g.nodes)
# Tested only with the following since I have pygraphviz not installed
pos = nx.kamada_kawai_layout(g)
# pos = pygraphviz_layout(G,prog="dot", args='-Gnodesep=10-Goverlap=false')
# changes back to original labels
nx.relabel_nodes(g, int_to_labels, copy=False)
label_pos = {label: pos[labels_to_int[label]] for label in g}
print(label_pos)
# {'Napoleon': array([0.73407672, 0.66096404]), 'Myriel': array([0.67744174, 0.53499379]), ....
print(g.nodes)
# ['Napoleon', 'Myriel', ...
您出錯的原因可能是pygraphviz
無法與networkx
不同的任意(可散列)節點networkx
。 因此,上面的代碼在調用布局之前簡單地將節點標簽轉換為int
並恢復節點和pos
dict 中的更改。
我發現使用任意可散列節點不適用於pygraphviz
后端,但它適用於pydot
:
import networkx as nx
from networkx.drawing.nx_pydot import graphviz_layout
g = ...
pos = graphviz_layout(g, "dot")
nx.draw_networkx(g, pos=pos)
這里的關鍵點是從networkx.drawing.nx_pydot
而不是networkx.drawing.nx_agraph
或其他地方導入graphviz_layout
。
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