How do I plot Shapely polygons and objects using Matplotlib?

Question

I want to use Shapely for my computational geometry project. I need to be able to visualize and display polygons, lines, and other geometric objects for this. I've tried to use Matplotlib for this but I am having trouble with it.

from shapely.geometry import Polygon
import matplotlib.pyplot as plt

polygon1 = Polygon([(0,5),
                    (1,1),
                    (3,0),
                    ])

plt.plot(polygon1)
plt.show()

I would like to be able to display this polygon in a plot. How would I change my code to do this?

1. Nicely written first question! 2. If you can get individual lists of the `x` and `y` coordinates for your polygon you can plot like: `plt.plot(polygon_x,polygon_y)`. You'll also have to append the first elements to the end to get the final line drawn. I unfortunately know nothing about shapely but hopefully this helps! — Hoog, Apr 04 '19 at 18:20
It would be `plt.plot(*polygon1.exterior.xy)`. More generally you can plot shapely objects through `descates`. Googling for "shapely matplotlib" should already give you relevant results. — ImportanceOfBeingErnest, Apr 04 '19 at 19:40
http://geopandas.org/ may be worth investigating for this functionality. — daryl, Apr 05 '19 at 05:32

score 71 · Accepted Answer · edited Dec 15 '19 at 20:58

71

Use:

import matplotlib.pyplot as plt

x,y = polygon1.exterior.xy
plt.plot(x,y)

Or, more succinctly:

plt.plot(*polygon1.exterior.xy)

edited Dec 15 '19 at 20:58

Nitay

3,223
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answered May 15 '19 at 00:10

ap21

1,490
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4

this doesn't work for objects with holes in it unfortunately – Allen Wang Feb 14 '20 at 22:31
3

If you want the interior rings (aka "holes") you can check from the `LinearRing`s in `polygon1.interiors`. – Brandt Apr 01 '20 at 19:13

score 13 · Answer 2 · answered Jul 10 '20 at 15:13

13

A little late but I find the most convenient way to do this is with Geopandas as suggested above but without writing to a file first.

from shapely.geometry import Polygon
import matplotlib.pyplot as plt
import geopandas as gpd

polygon1 = Polygon([(0,5),
                    (1,1),
                    (3,0),
                    ])

 p = gpd.GeoSeries(polygon1)
 p.plot()
 plt.show()

Checkout the docs for Geopandas.GeoSeries

answered Jul 10 '20 at 15:13

Micah Johnson

301
2
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The wrapping solution also helps to plot on a map: import mplleaflet; p.plot(); mplleaflet.show() – Ture Friese Nov 11 '20 at 11:54

score 7 · Answer 3 · answered Jan 10 '20 at 20:48

7

If your data is in a .shp file, I would recommend geopandas:

import geopandas as gpd
import matplotlib.pyplot as plt

shapefile = gpd.read_file("path/to/shapes.shp")
shapefile.plot()
plt.show()

answered Jan 10 '20 at 20:48

Mitchell Tracy

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Any way to plot this without writing to file first? – CGFoX Apr 29 '20 at 09:22
1

You may be able to get away with wrapping the string in a [StringIO](https://docs.python.org/3/library/io.html) as shown in [this question](https://stackoverflow.com/questions/141449/how-do-i-wrap-a-string-in-a-file-in-python), and passing the result to `gpd.read_file` though I have not tested this. – Mitchell Tracy Apr 30 '20 at 13:23

score 2 · Answer 4 · answered Apr 05 '19 at 14:00

2

It might be an overkill, but as an alternative to other good comments I would add an option of installing QGIS - a free software for working with geometries. All you need to do is to save your geometries as a shape file (.shp), geoJSON or any other format and open it with QGIS. If you're planning a big project it maybe more convenient at the end than using matplotlib.

answered Apr 05 '19 at 14:00

Marat Seroglazov

21
1

Thank you. I am building a project that visualizes the Ham Sandwich theorem for my computational geometry course. – ebeb9 Apr 13 '19 at 16:49

How do I plot Shapely polygons and objects using Matplotlib?

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