Shapefile To Network

Construct a network from shapefile and do analytics such as finding number of shortest paths from origin to destination, calculating centrality, degree of the nodes in network.

Overview

This python module allow you to get number of alpha times shortest paths from origin to destination where alpha is some constant specified by the user. You can also do some analysis over the network like finding degree, centrality of the nodes in graph.

Original Network

New Simplified Network

Installation

Install python >= 2.7

Ubuntu
```
$ sudo apt-get install python-2.7
```
Mac
```
$ brew install python
```

Run setup.py for installing required packages
```
$ python2.7 setup.py install
```

Documentation

Core Scripts

GraphConvertor.py - This module will take the input line shapefile and the path of output directory
ShortestPath.py - This module will calculate the number of alpha times shortest path from origin to destination in the graph

Other Scripts

BufferedGraph.py - This module create the square (buffer) of given size around the point geometry
GraphSimplify.py - This module will clean and remove all the redundant edges and extra/ uninformative nodes from the graph
MultiDiGraphConvertor.py - This module will convert the MultiDiGraph to SimpleGraph

How to use

Create the line shapefile of the road network (if not available)
- Using QGIS
  - Open the shapefile in QGIS which need to be converted to line shapefile
  - Go to Vector -> Geometry Tools and select Polygons to lines to convert shapefile into line shapefile
- Using python
  - Need to be implemented
Convert the created line shapefile into network using GraphConvertor.py
- Create GraphConvertor object by passing the path of input shapefile and the output directory
```
input_file  =  'path of the line shapefile'
output_dir  =  'path of directory to save new shapefiles'

graph_convertor_obj = GraphConvertor(input_file, output_dir)
```
- Call graph_convertor function to convert the input shapefile into road network and save the newly created shapefile into specifed output_dir along with list of nodes and edges in .csv files
```
network = graph_convertor_obj.graph_convertor()
```

Find number of shortest paths from origin to destination in new simplified network

Create ShortestPath object by passing all required parameters listed below

g            =  network
alpha        =  0.1
graph_buffer =  100
point_buffer =  50
break_point  =  200         # Upper limit to save computation time

shortest_path_obj   =  ShortestPath(g, alpha, graph_buffer, point_buffer, break_point)

Run alpha_times_shortestpath function to calculate number of paths which are alpha times the shortest path

start_tuple  =  (lat,lon)
end_tuple    =  (lat,lon)

total_path   =  shortest_path_obj.alpha_time_shortestpath(start_tuple, end_tuple)

Find metrics like degree centrality, closeness centrality, communicability and load centrality for doing analysis over created network.
- Create Centrality object by passing the network and the weight attribute of the network
```
centrality = Centrality(g, weight='distance')
```
- Get all the metrics of the network by calling metrics function of centrality class
```
degree_centrality, closeness_centrality, communicability, load_centrality = centrality.metrics()
```

More Info

For reference/citing: Journal Paper.

paulinkak / shapefile_to_network Goto Github PK