How to convert Numpy array to Panda DataFrame

问题

I have a Numpy array that looks like this:

[400.31865662]
[401.18514808]
[404.84015554]
[405.14682194]
[405.67735105]
[273.90969447]
[274.0894528]

When I try to convert it to a Panda Dataframe with the following code

y = pd.DataFrame(data)
print(y)

I get the following output when printing it. Why do I get all those zéros?

            0
0  400.318657
            0
0  401.185148
            0
0  404.840156
            0
0  405.146822
            0
0  405.677351
            0
0  273.909694
            0
0  274.089453

I would like to get a single column dataframe which looks like that:

400.31865662
401.18514808
404.84015554
405.14682194
405.67735105
273.90969447
274.0894528

回答1:

You could flatten the numpy array:

import numpy as np
import pandas as pd

data = [[400.31865662],
        [401.18514808],
        [404.84015554],
        [405.14682194],
        [405.67735105],
        [273.90969447],
        [274.0894528]]

arr = np.array(data)

df = pd.DataFrame(data=arr.flatten())

print(df)

Output

            0
0  400.318657
1  401.185148
2  404.840156
3  405.146822
4  405.677351
5  273.909694
6  274.089453

回答2:

I just figured out my mistake. (data) was a list of arrays:

[array([400.0290173]), array([400.02253235]), array([404.00252113]), array([403.99466754]), array([403.98681395]), array([271.97896036]), array([271.97110677])]

So I used np.vstack(data) to concatenate it

conc = np.vstack(data)

[[400.0290173 ]
 [400.02253235]
 [404.00252113]
 [403.99466754]
 [403.98681395]
 [271.97896036]
 [271.97110677]]

Then I convert the concatened array into a Pandas Dataframe by using the

newdf = pd.DataFrame(conc)


    0
0  400.029017
1  400.022532
2  404.002521
3  403.994668
4  403.986814
5  271.978960
6  271.971107

Et voilà!

回答3:

There is another way, which isn't mentioned in the other answers. If you have a NumPy array which is essentially a row vector (or column vector) i.e. shape like (n, ) , then you could do the following :

# sample array
x = np.zeros((20))
# empty dataframe
df = pd.DataFrame()
# add the array to df as a column
df['column_name'] = x

This way you can add multiple arrays as separate columns.

来源：https://stackoverflow.com/questions/53816008/how-to-convert-numpy-array-to-panda-dataframe

标签

python

pandas

numpy

type-conversion

numpy-ndarray