当前位置: 动力学知识库 > 问答 > 编程问答 >

python - Plotting Shapefiles which color decided by the scatter point data within

问题描述:

My question

Plotting heatmap with shapefile

1.intro

  • a bunch of shapefile represent the administration boundaries
  • a pandas.Dataframe containing some point with (longitude,latitude,value)

Code here:

 map = Basemap(llcrnrlon=xc1,llcrnrlat=yc1,urcrnrlon=xc2,urcrnrlat=yc2)

##Assuming "shape.shp" is my shapefile

map.readshapefile('./shape','shape',zorder =1,)

patches=[]

cs=plt.cm.Greens(np.arange(18)/18.)

for info, shape in zip(map.shape_info, map.shape):

x,y=zip(*shape)

patches.append( Polygon(np.array(shape), True) ) # facecolor= '#6582B3'

ax.add_collection(PatchCollection(patches, facecolor= cs,edgecolor='none',

linewidths=1.5, zorder=2))

## scatter the point, assuming "pt" is the Dataframe

pt_lat = pt.lat.as_matrix()

pt_lon = power.lon.as_matrix()

plt.scatter(pt_lon,pt_lat,marker='o',s=50,lw= 0,zorder = 3, alpha = 0.75)

Picture here:

http://i11.tietuku.com/9785abb6097b7c0e.png

2. My target

In the picture upward, the color of each shapefile is based on the colormap predefined.

  • Plotting Each area (In my case, 18 shapefile) with the color corresponding to the sum of pt.values within.
  • In other words, the inner point data decide the shapefile's color

Add --2015-01-11

Thanks for @MaxNoe's answer.

I have learned from your code, but still has some problem.

Here is my code & picture:

 fig = plt.figure(figsize =(8,6))

ax = plt.subplot()

map = Basemap(llcrnrlon=xc1,llcrnrlat=yc1,urcrnrlon=xc2,urcrnrlat=yc2)

map.readshapefile('./shape','shape')

patches=[]

for info, shape in zip(map.shape_info, map.shape):

x,y=zip(*shape)

patches.append(Polygon(np.array(shape), True) )

xx = pt.lon.iloc[:].as_matrix()

yy = pt.lat.iloc[:].as_matrix()

value = pt.value.iloc[:].as_matrix()

sh = (len(xx),2)

position = np.zeros(len(xx)*2).reshape(*sh)

for i in range(0,len(xx),1):

position[i] = np.array([xx[i],yy[i]])

poly_values = []

for patch in patches:

mask = np.array([patch.contains_point(xy) for xy in position])

poly_values.append(value[mask].sum())

coll = PatchCollection(patches, cmap = 'Greens')

coll.set_array(np.array(poly_values))

ax.add_collection(coll)

plt.colorbar(coll,label = "polygon")

point_plot = plt.scatter(xx,yy,marker='o',s=80,lw= 0,zorder = 3, c = "r",alpha = 0.75)

ax.set_frame_on(False)

divider = make_axes_locatable(ax)

cax = divider.append_axes("right", size="4%", pad=0.1)

cbar = plt.colorbar(coll,label = "polygon",cax= cax)

http://i4.tietuku.com/9a7b0cbc16f2e0b0.png

  • It seems like the color for polygon[i] isn't according to the poly_value[i]
  • I think the problem is coll.set_array doesn't work.
  • Otherwise, I have checked each polygon and the scatter point value within, the poly_value[i] and the actual condition is not match(bigger than reality). I think the I may use value.mask wrong.

网友答案:
  • You can use Polygon.contains_point to check if a point is inside it.

  • I use this function to create a boolean mask to address the points which are inside that poly and use .sum() to get the value for this polygon.

  • Then I use PatchCollection.set_array to set the values.

Here is the code (without basemap as I do not have the shape file):

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.patches import Polygon
from matplotlib.collections import PatchCollection

# some random numbers for demonstration
data = np.random.normal(0, 1, (100, 2))
value = np.random.normal(0, 1, 100)

polygons = [
    Polygon([(0, 0), (0, 3), (-3, 3), (-3, 0)], closed=True),
    Polygon([(0, 0), (0, -3), (-3, -3), (-3, 0)], closed=True),
    Polygon([(0, 0), (0, 3), (3, 3), (3, 0)], closed=True),
    Polygon([(0, 0), (0, -3), (3, -3), (3, 0)], closed=True),
]


poly_values = []
for poly in polygons:
    mask = np.array([poly.contains_point(xy) for xy in data])
    poly_values.append(value[mask].sum())


coll = PatchCollection(polygons, cmap='magma')
coll.set_array(np.array(poly_values))

fig, ax = plt.subplots()
ax.add_collection(coll)
points = ax.scatter(data[:, 0], data[:, 1], c=value, cmap='viridis', linewidth=0)
fig.colorbar(coll, label='polygons')
fig.colorbar(points, label='points')
plt.show()

Result:

分享给朋友:
您可能感兴趣的文章:
随机阅读: