xarray （教程）第二章数据结构

最新推荐文章于 2025-03-11 10:04:49 发布

西大·阿志

最新推荐文章于 2025-03-11 10:04:49 发布

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分类专栏： xarray使用教程文章标签： python

本文链接：https://blog.youkuaiyun.com/qq_46608464/article/details/135546479

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数据结构

DataArray

DataArray是xarray对带标签的多维数组的实现。
它有几个关键属性:

values:保存数组值的numpy.ndarray或类似numpy的数组
dims:每个轴的尺寸名称(例如，(’ x ‘，’ y ‘，’ z '))
coords:一个类似dict的数组(坐标)容器，用来标记每个点(例如，一维数组的数字、日期对象或字符串)
attrs:保存任意元数据(属性)的dict

Creating a DataArray

DataArray构造函数采用:

数据:值的多维数组(例如，numpy ndarray、类似numpy的数组、Series、DataFrame或pandas。面板)
坐标表:坐标表或坐标字典。如果是列表，应该是元组列表，其中第一个元素是维度名称，第二个元素是对应的坐标array_like对象。
dims:维度名称列表。如果省略，并且coords是元组列表，则维度名称取自coords。
attrs:要添加到实例的属性字典
name:命名实例的字符串

import xarray as xr
import numpy as np
import pandas as pd
data = np.random.rand(4, 3)

locs = ["IA", "IL", "IN"]

times = pd.date_range("2000-01-01", periods=4)

foo = xr.DataArray(data, coords=[times, locs], dims=["time", "space"])

print(foo)
"""
<xarray.DataArray (time: 4, space: 3)>
array([[0.35200563, 0.569955  , 0.98816514],
       [0.95311654, 0.8268097 , 0.15125512],
       [0.6361332 , 0.35353079, 0.33760348],
       [0.28808098, 0.19150729, 0.79793025]])
Coordinates:
  * time     (time) datetime64[ns] 2000-01-01 2000-01-02 2000-01-03 2000-01-04
  * space    (space) <U2 'IA' 'IL' 'IN'
"""

DataArray properties

import xarray as xr
import numpy as np
import pandas as pd
data = np.random.rand(4, 3)

locs = ["IA", "IL", "IN"]

times = pd.date_range("2000-01-01", periods=4)

foo = xr.DataArray(data, coords=[times, locs], dims=["time1", "space1"])
print(foo.values)

print(foo.dims)

print(foo.coords)

print(foo.attrs)

print(foo.name)
"""
[[0.90006724 0.52320969 0.54733588]
 [0.1018204  0.65948629 0.52749082]
 [0.73632638 0.50559387 0.57415316]
 [0.24010929 0.52222784 0.39407124]]
('time1', 'space1')
Coordinates:
  * time1    (time1) datetime64[ns] 2000-01-01 2000-01-02 2000-01-03 2000-01-04
  * space1   (space1) <U2 'IA' 'IL' 'IN'
{}
None
"""

foo.name = "foo"

foo.attrs["units"] = "meters"

foo

"""
<xarray.DataArray 'foo' (time: 4, space: 3)>
array([[0.127, 0.967, 0.26 ],
       [0.897, 0.377, 0.336],
       [0.451, 0.84 , 0.123],
       [0.543, 0.373, 0.448]])
Coordinates:
  * time     (time) datetime64[ns] 2000-01-01 2000-01-02 2000-01-03 2000-01-04
  * space    (space) <U2 'IA' 'IL' 'IN'
Attributes:
    units:    meters
"""
foo.rename("bar")
"""
<xarray.DataArray 'bar' (time: 4, space: 3)>
array([[0.127, 0.967, 0.26 ],
       [0.897, 0.377, 0.336],
       [0.451, 0.84 , 0.123],
       [0.543, 0.373, 0.448]])
Coordinates:
  * time     (time) datetime64[ns] 2000-01-01 2000-01-02 2000-01-03 2000-01-04
  * space    (space) <U2 'IA' 'IL' 'IN'
Attributes:
    units:    meters
"""

DataArray Coordinates


foo.coords["time"]
"""
<xarray.DataArray 'time' (time: 4)>
array(['2000-01-01T00:00:00.000000000', '2000-01-02T00:00:00.000000000',
       '2000-01-03T00:00:00.000000000', '2000-01-04T00:00:00.000000000'],
      dtype='datetime64[ns]')
Coordinates:
  *