Python 将数据帧转换为NumPy数组
我很想知道如何将pandas数据帧转换为NumPy数组 数据帧:Python 将数据帧转换为NumPy数组,python,arrays,pandas,numpy,dataframe,Python,Arrays,Pandas,Numpy,Dataframe,我很想知道如何将pandas数据帧转换为NumPy数组 数据帧: import numpy as np import pandas as pd index = [1, 2, 3, 4, 5, 6, 7] a = [np.nan, np.nan, np.nan, 0.1, 0.1, 0.1, 0.1] b = [0.2, np.nan, 0.2, 0.2, 0.2, np.nan, np.nan] c = [np.nan, 0.5, 0.5, np.nan, 0.5, 0.5, np.nan]
import numpy as np
import pandas as pd
index = [1, 2, 3, 4, 5, 6, 7]
a = [np.nan, np.nan, np.nan, 0.1, 0.1, 0.1, 0.1]
b = [0.2, np.nan, 0.2, 0.2, 0.2, np.nan, np.nan]
c = [np.nan, 0.5, 0.5, np.nan, 0.5, 0.5, np.nan]
df = pd.DataFrame({'A': a, 'B': b, 'C': c}, index=index)
df = df.rename_axis('ID')
给予
我想将其转换为NumPy数组,如下所示:
array([[ nan, 0.2, nan],
[ nan, nan, 0.5],
[ nan, 0.2, 0.5],
[ 0.1, 0.2, nan],
[ 0.1, 0.2, 0.5],
[ 0.1, nan, 0.5],
[ 0.1, nan, nan]])
我该怎么做
作为奖励,可以像这样保存数据类型吗
array([[ 1, nan, 0.2, nan],
[ 2, nan, nan, 0.5],
[ 3, nan, 0.2, 0.5],
[ 4, 0.1, 0.2, nan],
[ 5, 0.1, 0.2, 0.5],
[ 6, 0.1, nan, 0.5],
[ 7, 0.1, nan, nan]],
dtype=[('ID', '<i4'), ('A', '<f8'), ('B', '<f8'), ('B', '<f8')])
数组([[1,nan,0.2,nan],
[2,楠,楠,0.5],
[3,nan,0.2,0.5],
[4,0.1,0.2,nan],
[ 5, 0.1, 0.2, 0.5],
[6,0.1,nan,0.5],,
[7,0.1,楠,楠]],
dtype=[('ID','您可以使用to_records
方法,但如果数据类型不是您想要的,则必须对其进行一些处理。在我的例子中,从字符串复制DF后,索引类型是string(在pandas中由对象
dtype表示):
[102]中的:df
出[102]:
标签A B C
身份证件
1 NaN 0.2 NaN
2楠楠0.5
3.0.20.5
40.10.2南
5 0.1 0.2 0.5
6 0.1 NaN 0.5
7 0.1楠楠
在[103]中:df.index.dtype
Out[103]:数据类型(“对象”)
In[104]:df.to_记录()
Out[104]:
记录数组([(1,nan,0.2,nan),(2,nan,nan,0.5),(3,nan,0.2,0.5),
(4,0.1,0.2,nan),(5,0.1,0.2,0.5),(6,0.1,nan,0.5),
(7,0.1,nan,nan),,
dtype=[('index','O8'),('A','您可以使用to_records
方法,但如果数据类型不是您想要的,则必须对其进行一些处理。在我的例子中,从字符串复制DF后,索引类型是字符串(在pandas中由对象
dtype表示):
[102]中的:df
出[102]:
标签A B C
身份证件
1 NaN 0.2 NaN
2楠楠0.5
3.0.20.5
40.10.2南
5 0.1 0.2 0.5
6 0.1 NaN 0.5
7 0.1楠楠
在[103]中:df.index.dtype
Out[103]:数据类型(“对象”)
In[104]:df.to_记录()
Out[104]:
记录数组([(1,nan,0.2,nan),(2,nan,nan,0.5),(3,nan,0.2,0.5),
(4,0.1,0.2,nan),(5,0.1,0.2,0.5),(6,0.1,nan,0.5),
(7,0.1,nan,nan),,
dtype=[('index','O8'),('A','我只需将and函数链接起来,以获得数据帧的Numpy表示形式,包括索引:
In [8]: df
Out[8]:
A B C
0 -0.982726 0.150726 0.691625
1 0.617297 -0.471879 0.505547
2 0.417123 -1.356803 -1.013499
3 -0.166363 -0.957758 1.178659
4 -0.164103 0.074516 -0.674325
5 -0.340169 -0.293698 1.231791
6 -1.062825 0.556273 1.508058
7 0.959610 0.247539 0.091333
[8 rows x 3 columns]
In [9]: df.reset_index().values
Out[9]:
array([[ 0. , -0.98272574, 0.150726 , 0.69162512],
[ 1. , 0.61729734, -0.47187926, 0.50554728],
[ 2. , 0.4171228 , -1.35680324, -1.01349922],
[ 3. , -0.16636303, -0.95775849, 1.17865945],
[ 4. , -0.16410334, 0.0745164 , -0.67432474],
[ 5. , -0.34016865, -0.29369841, 1.23179064],
[ 6. , -1.06282542, 0.55627285, 1.50805754],
[ 7. , 0.95961001, 0.24753911, 0.09133339]])
要获取数据类型,我们需要使用以下命令将此数据数组转换为结构化数组:
[10]中的:df.reset_index().values.ravel().view(数据类型=[('index',int),('A',float),('B',float),('C',float)])
出[10]:
数组([(0,-0.98272574,0.150726,0.69162512),
( 1, 0.61729734, -0.47187926, 0.50554728),
( 2, 0.4171228 , -1.35680324, -1.01349922),
( 3, -0.16636303, -0.95775849, 1.17865945),
( 4, -0.16410334, 0.0745164 , -0.67432474),
( 5, -0.34016865, -0.29369841, 1.23179064),
( 6, -1.06282542, 0.55627285, 1.50805754),
( 7, 0.95961001, 0.24753911, 0.09133339),
dtype=[('index','我只需将和函数链接起来,以获得数据帧的Numpy表示形式,包括索引:
In [8]: df
Out[8]:
A B C
0 -0.982726 0.150726 0.691625
1 0.617297 -0.471879 0.505547
2 0.417123 -1.356803 -1.013499
3 -0.166363 -0.957758 1.178659
4 -0.164103 0.074516 -0.674325
5 -0.340169 -0.293698 1.231791
6 -1.062825 0.556273 1.508058
7 0.959610 0.247539 0.091333
[8 rows x 3 columns]
In [9]: df.reset_index().values
Out[9]:
array([[ 0. , -0.98272574, 0.150726 , 0.69162512],
[ 1. , 0.61729734, -0.47187926, 0.50554728],
[ 2. , 0.4171228 , -1.35680324, -1.01349922],
[ 3. , -0.16636303, -0.95775849, 1.17865945],
[ 4. , -0.16410334, 0.0745164 , -0.67432474],
[ 5. , -0.34016865, -0.29369841, 1.23179064],
[ 6. , -1.06282542, 0.55627285, 1.50805754],
[ 7. , 0.95961001, 0.24753911, 0.09133339]])
要获取数据类型,我们需要使用以下命令将此数据数组转换为结构化数组:
<代码>在[10]:df.reset\u index().values.ravel()。视图(dtype=[('index',int),('A',float),('B',float),('C',float)])
出[10]:
数组([(0,-0.98272574,0.150726,0.69162512),
( 1, 0.61729734, -0.47187926, 0.50554728),
( 2, 0.4171228 , -1.35680324, -1.01349922),
( 3, -0.16636303, -0.95775849, 1.17865945),
( 4, -0.16410334, 0.0745164 , -0.67432474),
( 5, -0.34016865, -0.29369841, 1.23179064),
( 6, -1.06282542, 0.55627285, 1.50805754),
( 7, 0.95961001, 0.24753911, 0.09133339),
dtype=[('index','注意:此答案中使用的.as_matrix()
方法已被弃用。0.23.4警告:
方法.as_matrix
将在将来的版本中删除。请改用.values
熊猫有内在的东西
numpy_matrix = df.as_matrix()
给予
注意:此答案中使用的.as_matrix()
方法已被弃用。0.23.4警告:
方法.as_matrix
将在将来的版本中删除。请改用.values
熊猫有内在的东西
numpy_matrix = df.as_matrix()
给予
下面是我从数据帧生成结构数组的方法
def df_to_sarray(df):
"""
Convert a pandas DataFrame object to a numpy structured array.
This is functionally equivalent to but more efficient than
np.array(df.to_array())
:param df: the data frame to convert
:return: a numpy structured array representation of df
"""
v = df.values
cols = df.columns
if six.PY2: # python 2 needs .encode() but 3 does not
types = [(cols[i].encode(), df[k].dtype.type) for (i, k) in enumerate(cols)]
else:
types = [(cols[i], df[k].dtype.type) for (i, k) in enumerate(cols)]
dtype = np.dtype(types)
z = np.zeros(v.shape[0], dtype)
for (i, k) in enumerate(z.dtype.names):
z[k] = v[:, i]
return z
创建数据帧
import pandas as pd
import numpy as np
import six
NaN = float('nan')
ID = [1, 2, 3, 4, 5, 6, 7]
A = [NaN, NaN, NaN, 0.1, 0.1, 0.1, 0.1]
B = [0.2, NaN, 0.2, 0.2, 0.2, NaN, NaN]
C = [NaN, 0.5, 0.5, NaN, 0.5, 0.5, NaN]
columns = {'A':A, 'B':B, 'C':C}
df = pd.DataFrame(columns, index=ID)
df.index.name = 'ID'
print(df)
A B C
ID
1 NaN 0.2 NaN
2 NaN NaN 0.5
3 NaN 0.2 0.5
4 0.1 0.2 NaN
5 0.1 0.2 0.5
6 0.1 NaN 0.5
7 0.1 NaN NaN
定义从数据帧生成numpy结构数组(不是记录数组)的函数
def df_to_sarray(df):
"""
Convert a pandas DataFrame object to a numpy structured array.
This is functionally equivalent to but more efficient than
np.array(df.to_array())
:param df: the data frame to convert
:return: a numpy structured array representation of df
"""
v = df.values
cols = df.columns
if six.PY2: # python 2 needs .encode() but 3 does not
types = [(cols[i].encode(), df[k].dtype.type) for (i, k) in enumerate(cols)]
else:
types = [(cols[i], df[k].dtype.type) for (i, k) in enumerate(cols)]
dtype = np.dtype(types)
z = np.zeros(v.shape[0], dtype)
for (i, k) in enumerate(z.dtype.names):
z[k] = v[:, i]
return z
使用reset_index
创建一个新的数据框,其中包含索引作为其数据的一部分。将该数据框转换为结构数组
sa = df_to_sarray(df.reset_index())
sa
array([(1L, nan, 0.2, nan), (2L, nan, nan, 0.5), (3L, nan, 0.2, 0.5),
(4L, 0.1, 0.2, nan), (5L, 0.1, 0.2, 0.5), (6L, 0.1, nan, 0.5),
(7L, 0.1, nan, nan)],
dtype=[('ID', '<i8'), ('A', '<f8'), ('B', '<f8'), ('C', '<f8')])
sa=df\u to\u sarray(df.reset\u index())
sa
数组([(1L,nan,0.2,nan),(2L,nan,nan,0.5),(3L,nan,0.2,0.5),
(4L,0.1,0.2,nan),(5L,0.1,0.2,0.5),(6L,0.1,nan,0.5),
(7L,0.1,nan,nan)],
dtype=[('ID','以下是我从数据帧生成结构数组的方法
def df_to_sarray(df):
"""
Convert a pandas DataFrame object to a numpy structured array.
This is functionally equivalent to but more efficient than
np.array(df.to_array())
:param df: the data frame to convert
:return: a numpy structured array representation of df
"""
v = df.values
cols = df.columns
if six.PY2: # python 2 needs .encode() but 3 does not
types = [(cols[i].encode(), df[k].dtype.type) for (i, k) in enumerate(cols)]
else:
types = [(cols[i], df[k].dtype.type) for (i, k) in enumerate(cols)]
dtype = np.dtype(types)
z = np.zeros(v.shape[0], dtype)
for (i, k) in enumerate(z.dtype.names):
z[k] = v[:, i]
return z
创建数据帧
import pandas as pd
import numpy as np
import six
NaN = float('nan')
ID = [1, 2, 3, 4, 5, 6, 7]
A = [NaN, NaN, NaN, 0.1, 0.1, 0.1, 0.1]
B = [0.2, NaN, 0.2, 0.2, 0.2, NaN, NaN]
C = [NaN, 0.5, 0.5, NaN, 0.5, 0.5, NaN]
columns = {'A':A, 'B':B, 'C':C}
df = pd.DataFrame(columns, index=ID)
df.index.name = 'ID'
print(df)
A B C
ID
1 NaN 0.2 NaN
2 NaN NaN 0.5
3 NaN 0.2 0.5
4 0.1 0.2 NaN
5 0.1 0.2 0.5
6 0.1 NaN 0.5
7 0.1 NaN NaN
定义从数据帧生成numpy结构数组(不是记录数组)的函数
def df_to_sarray(df):
"""
Convert a pandas DataFrame object to a numpy structured array.
This is functionally equivalent to but more efficient than
np.array(df.to_array())
:param df: the data frame to convert
:return: a numpy structured array representation of df
"""
v = df.values
cols = df.columns
if six.PY2: # python 2 needs .encode() but 3 does not
types = [(cols[i].encode(), df[k].dtype.type) for (i, k) in enumerate(cols)]
else:
types = [(cols[i], df[k].dtype.type) for (i, k) in enumerate(cols)]
dtype = np.dtype(types)
z = np.zeros(v.shape[0], dtype)
for (i, k) in enumerate(z.dtype.names):
z[k] = v[:, i]
return z
使用reset_index
创建一个新的数据框,其中包含索引作为其数据的一部分。将该数据框转换为结构数组
sa = df_to_sarray(df.reset_index())
sa
array([(1L, nan, 0.2, nan), (2L, nan, nan, 0.5), (3L, nan, 0.2, 0.5),
(4L, 0.1, 0.2, nan), (5L, 0.1, 0.2, 0.5), (6L, 0.1, nan, 0.5),
(7L, 0.1, nan, nan)],
dtype=[('ID', '<i8'), ('A', '<f8'), ('B', '<f8'), ('C', '<f8')])
sa=df\u to\u sarray(df.reset\u index())
sa
数组([(1L,nan,0.2,nan),(2L,nan,nan,0.5),(3L,nan,0.2,0.5),
(4L,0.1,0.2,nan),(5L,0.1,0.2,0.5),(6L,0.1,nan,0.5),
(7L,0.1,nan,nan)],
dtype=[('ID','在meteore的回答之后,我找到了代码
df.index = df.index.astype('i8')
不适合我。所以我把我的代码放在这里是为了方便其他遇到这个问题的人
city_cluster_df = pd.read_csv(text_filepath, encoding='utf-8')
# the field 'city_en' is a string, when converted to Numpy array, it will be an object
city_cluster_arr = city_cluster_df[['city_en','lat','lon','cluster','cluster_filtered']].to_records()
descr=city_cluster_arr.dtype.descr
# change the field 'city_en' to string type (the index for 'city_en' here is 1 because before the field is the row index of dataframe)
descr[1]=(descr[1][0], "S20")
newArr=city_cluster_arr.astype(np.dtype(descr))
根据Metore的回答,我找到了密码
df.index = df.index.astype('i8')
不适合我。所以我把我的代码放在这里是为了方便其他遇到这个问题的人
city_cluster_df = pd.read_csv(text_filepath, encoding='utf-8')
# the field 'city_en' is a string, when converted to Numpy array, it will be an object
city_cluster_arr = city_cluster_df[['city_en','lat','lon','cluster','cluster_filtered']].to_records()
descr=city_cluster_arr.dtype.descr
# change the field 'city_en' to string type (the index for 'city_en' here is 1 because before the field is the row index of dataframe)
descr[1]=(descr[1][0], "S20")
newArr=city_cluster_arr.astype(np.dtype(descr))
要将熊猫数据帧(df)转换为numpy数据阵列,请使用以下代码:
df.values
array([[nan, 0.2, nan],
[nan, nan, 0.5],
[nan, 0.2, 0.5],
[0.1, 0.2, nan],
[0.1, 0.2, 0.5],
[0.1, nan, 0.5],
[0.1, nan, nan]])
要将熊猫数据帧(df)转换为numpy数据阵列,请使用以下代码:
df.values
array([[nan, 0.2, nan],
[nan, nan, 0.5],
[nan, 0.2, 0.5],
[0.1, 0.2, nan],
[0.1, 0.2, 0.5],
[0.1, nan, 0.5],
[0.1, nan, nan]])
在从dataframe导出到arcgis表和stum时遇到了类似的问题
# Setup
df = pd.DataFrame(data={'A': [1, 2, 3], 'B': [4, 5, 6], 'C': [7, 8, 9]},
index=['a', 'b', 'c'])
# Convert the entire DataFrame
df.to_numpy()
# array([[1, 4, 7],
# [2, 5, 8],
# [3, 6, 9]])
# Convert specific columns
df[['A', 'C']].to_numpy()
# array([[1, 7],
# [2, 8],
# [3, 9]])
df.index.to_numpy()
# array(['a', 'b', 'c'], dtype=object)
df['A'].to_numpy()
# array([1, 2, 3])
v = df.to_numpy()
v[0, 0] = -1
df
A B C
a -1 4 7
b 2 5 8
c 3 6 9
a = pd.array([1, 2, None], dtype="Int64")
a
<IntegerArray>
[1, 2, <NA>]
Length: 3, dtype: Int64
# Wrong
a.to_numpy()
# array([1, 2, <NA>], dtype=object) # yuck, objects
# Correct
a.to_numpy(dtype='float', na_value=np.nan)
# array([ 1., 2., nan])
# Also correct
a.to_numpy(dtype='int', na_value=-1)
# array([ 1, 2, -1])
df.to_records()
# rec.array([('a', 1, 4, 7), ('b', 2, 5, 8), ('c', 3, 6, 9)],
# dtype=[('index', 'O'), ('A', '<i8'), ('B', '<i8'), ('C', '<i8')])
v = df.reset_index()
np.rec.fromrecords(v, names=v.columns.tolist())
# rec.array([('a', 1, 4, 7), ('b', 2, 5, 8), ('c', 3, 6, 9)],
# dtype=[('index', '<U1'), ('A', '<i8'), ('B', '<i8'), ('C', '<i8')])
df2 = pd.concat([df] * 10000)
%timeit df2.to_records()
%%timeit
v = df2.reset_index()
np.rec.fromrecords(v, names=v.columns.tolist())
12.9 ms ± 511 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)
9.56 ms ± 291 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)
a = numpy.asarray(df)
import pandas as pd
df = pd.DataFrame({"A": [1, 2], "B": [3, 4]})
df_to_array = df.to_numpy()
array([[1, 3],
[2, 4]])
np.array(df)
array([['ID', nan, nan, nan],
['1', nan, 0.2, nan],
['2', nan, nan, 0.5],
['3', nan, 0.2, 0.5],
['4', 0.1, 0.2, nan],
['5', 0.1, 0.2, 0.5],
['6', 0.1, nan, 0.5],
['7', 0.1, nan, nan]], dtype=object)