Pandas 如何找出哪些管道朝向错误的方向

我正在计算区域供暖系统。我从shapefile中获取信息–对于管道，我有一个带有起点和终点坐标的线串几何体。我创建了一个geopandas数据帧：

+-------+----------------------------------------------------------------------------------------------------------------------+
|       |                                                                                                                      |
| ID    | geometry                                                                                                             |
+-------+----------------------------------------------------------------------------------------------------------------------+
|       |                                                                                                                      |
| 0     | LINESTRING (1679896.423 5802688.586,   1679896.034 5802688.745)                                                      |
+-------+----------------------------------------------------------------------------------------------------------------------+
|       |                                                                                                                      |
| 1     | LINESTRING (1679896.034 5802688.745, 1679892.419 5802689.660)                                                        |
+-------+----------------------------------------------------------------------------------------------------------------------+
|       |                                                                                                                      |
| 2     | LINESTRING (1679908.185 5802692.533, 1679911.830 5802691.936,   1679927.258 5802689.562, 1679945.682 5802686.042)    |
+-------+----------------------------------------------------------------------------------------------------------------------+
|       |                                                                                                                      |
| 3     | LINESTRING (1679945.667 5802685.478, 1679945.653 5802685.247)                                                        |
+-------+----------------------------------------------------------------------------------------------------------------------+
|       |                                                                                                                      |
| 4     | ….                                                                                                                   |
+-------+----------------------------------------------------------------------------------------------------------------------+

对于计算，我必须确定线之间的所有连接（当前管道必须定义“上一个管道”和“下一个管道”）。我这样做的方式是，我创建了一个linestring的起点和终点，并将dataframe与自身合并（将终点与起点配对）。问题是，一些线串（大约占所有线串的1/5）朝向错误的方向，所以我只得到它们的NaN结果（因为当前管道的终点不接触下一个管道的起点，而只是另一个终点）

另外一个问题是，有10个管道连续朝着错误的方向（所以在它们之间，我实际上得到了结果，但它们是错误的）——另一个问题是，有时PipeNext是NaN，因为当前行是终点线。 有没有办法确定管道朝向错误的方向？如果没有，是否可以在绘图上显示线的方向

编辑-添加当前代码：

import pandas as pd
import geopandas as gpd
import folium

import shapefile
import matplotlib.pyplot as plt
from geopandas import GeoDataFrame
import contextily as ctx
df_pipes=gpd.read_file("DO_Hrastnik_odsek.shp")
df_user=gpd.read_file("DO_Hrastnik_objekt.shp")

df_pipes.crs = {'init': 'epsg:3912'}
df_pipes=df_pipes.to_crs("EPSG:3857")
df_user.crs = {'init': 'epsg:3912'}
df_user=df_user.to_crs("EPSG:3857")

df_pipes["ID"] = df_pipes.index + 1
df_pipes['ID']=df_pipes['ID'].astype(str)

df_pipes=df_pipes[["geometry","ID","LENGTH_3D"]].copy()

from shapely.geometry import Point, LineString

df_pipes["node_ups"] = gpd.GeoSeries([Point(list(pt['geometry'].coords)[0]) for i,pt in df_pipes.iterrows()])
df_pipes["node_dws"] = gpd.GeoSeries([Point(list(pt['geometry'].coords)[-1]) for i,pt in df_pipes.iterrows()])

tmp = df_pipes[['ID', 'node_dws', 'node_ups']]

df_connections=pd.merge(tmp, tmp, left_on='node_dws', right_on='node_ups',how="outer")
df_connections=pd.merge(df_connections, tmp, left_on='node_ups_x', right_on='node_dws',how="outer")

df_connections.drop(['node_dws_y', 'node_ups_y','node_dws', 'node_ups'], axis=1, inplace=True)

df_connections = df_connections[df_connections['ID_x'].notna()]

df_connections = df_connections.rename(columns={'ID_x': 'ID_pipe', 'node_dws_x': 'node_dws','node_ups_x': 'node_ups', 'ID_y': 'pipeNext','ID': 'pipePrevious'})

tmp = df_connections[['ID_pipe', 'pipeNext', 'pipePrevious']]
df_connections=pd.merge(tmp, df_pipes, left_on='ID_pipe', right_on='ID',how="outer")

---

您从评论中了解到的检查端点在何处相遇的想法是一种方法，它并不像您所说的那么复杂。从网络的起始管道开始（所有水都来自于此–我假设这是一根管道），然后使用递归函数沿着网络向下移动：

from shapely.geometry import Point, LineString # You can delete your own code after this line.

# df.apply is faster than iterrows, so I rewrote the following two lines
df_pipes['node_ups'] = df_pipes.geometry.apply(lambda linestring: Point(list(linestring.coords)[0])
df_pipes['node_dws'] = df_pipes.geometry.apply(lambda linestring: Point(list(linestring.coords)[-1])

def check_downstream(pipe_id, pipes):
    """Set next and previous pipe ID for all downstream pipes"""

    endpoint = pipes.loc[pipe_id, 'node_dws']
    next_ids = list(pipes['node_ups' == endpoint]['ID'])
    reversed_ids = list(pipes[(pipes['node_dws'] == endpoint) & (pipes['ID'] != pipe_id)]['ID'])
    for rev_id in reversed_ids:
        pipes.loc[rev_id, 'node_ups'], pipes.loc[rev_id, 'node_dws'] = pipes.loc[rev_id, 'node_dws'], pipes.loc[rev_id, 'node_ups']
    next_ids = next_ids + reversed_ids
    for nxt_id in next_ids:
        pipes.loc[pipe_id, 'pipeNext'] = nxt_id
        pipes.loc[nxt_id, 'pipePrevious'] = pipe_id
        check_downstream(nxt_id, pipes) # This is the recursive function call.


df_connections = df_pipes.copy()
df_connections['pipePrevious'] = 'undetermined'
df_connections['pipeNext'] = 'undetermined'

first_id = 99 # or whatever it is
check_downstream(first_id, df_connections)

---

请注意，这不会反转线条本身，但如果需要，您也可以这样做。

是否可以测试线条的一点是否与起点或终点匹配？这并不是说你的管道包含坡度什么的，它只是线条信息，所以就这样对待它。@Maartenverman问题是，在某个地方有多条连续的线条朝向错误的方向。在它们之间，我们可以看到邻居的下一个和上一个被切换（他们的方向是上游）。你能画一个小图吗？概述您的问题。@Maartenverman-以下是系统的一部分：。黄线是错误的方向线。我曾经考虑过这样做：如果内点（currentID）遇到（endpointNEXTID）、交换值（endpointNEXTID startpointNEXTID）、中断、重新启动循环，这将逐行旋转，但考虑到分支结构，这看起来非常复杂。您能给我们展示一下您的代码吗？如果我们可以看到您是如何到达第二个数据帧的，以及可以调整哪些内容来纠正它，那么我们就可以更容易地提供帮助。

from shapely.geometry import Point, LineString # You can delete your own code after this line.

# df.apply is faster than iterrows, so I rewrote the following two lines
df_pipes['node_ups'] = df_pipes.geometry.apply(lambda linestring: Point(list(linestring.coords)[0])
df_pipes['node_dws'] = df_pipes.geometry.apply(lambda linestring: Point(list(linestring.coords)[-1])

def check_downstream(pipe_id, pipes):
    """Set next and previous pipe ID for all downstream pipes"""

    endpoint = pipes.loc[pipe_id, 'node_dws']
    next_ids = list(pipes['node_ups' == endpoint]['ID'])
    reversed_ids = list(pipes[(pipes['node_dws'] == endpoint) & (pipes['ID'] != pipe_id)]['ID'])
    for rev_id in reversed_ids:
        pipes.loc[rev_id, 'node_ups'], pipes.loc[rev_id, 'node_dws'] = pipes.loc[rev_id, 'node_dws'], pipes.loc[rev_id, 'node_ups']
    next_ids = next_ids + reversed_ids
    for nxt_id in next_ids:
        pipes.loc[pipe_id, 'pipeNext'] = nxt_id
        pipes.loc[nxt_id, 'pipePrevious'] = pipe_id
        check_downstream(nxt_id, pipes) # This is the recursive function call.


df_connections = df_pipes.copy()
df_connections['pipePrevious'] = 'undetermined'
df_connections['pipeNext'] = 'undetermined'

first_id = 99 # or whatever it is
check_downstream(first_id, df_connections)