Read fields from vector

This example shows how to read fields values from a vector file.

Import librairies

import museotoolbox as mtb

Load HistoricalMap dataset

raster,vector = mtb.datasets.load_historical_data(low_res=True)

Note

If you have no memories on what the fields name are, simply put the vector path

try :
    mtb.processing.read_vector_values(vector)
except Exception as e:
    print(e)

Out:

These fields are available : ['Class', 'Type', 'uniquefid']

Read values from field ‘Class’

Y,Name = mtb.processing.read_vector_values(vector,'Class','Type')
print(Y,Name)
print(Y.shape)

Out:

[1 1 1 1 2 2 2 1 1 2 4 5 4 5 3 3 3] ['Forest' 'Forest' 'Forest' 'Forest' 'Agriculture' 'Agriculture'
 'Agriculture' 'Forest' 'Forest' 'Agriculture' 'Water' 'Buildings' 'Water'
 'Buildings' 'Soil' 'Soil' 'Soil']
(17,)

Read values from field beginning with ‘C’

As multiple fields can begin with C, function returns a column per field

C = mtb.processing.read_vector_values(vector,band_prefix='C')
print(C)
print(C.shape)

Out:

[[1]
 [1]
 [1]
 [1]
 [2]
 [2]
 [2]
 [1]
 [1]
 [2]
 [4]
 [5]
 [4]
 [5]
 [3]
 [3]
 [3]]
(17, 1)

from matplotlib import pyplot as plt
import numpy as np
plt.title('Number of polygons per label')
plt.bar(np.arange(np.unique(Y).size)+1,np.unique(Y,return_counts=True)[1])

Out:

<BarContainer object of 5 artists>