将天数 Int64 转换为日期

Question

我需要将以下数据框（天）转换为物理日期。当 (days=0) 这是基准年 01/01/1960。您能否协助将天数列（从 1960 年 1 月 1 日开始的天数）转换回日期？

df=pd.DataFrame([-730,-640,-549,457,-365,275,-184,-92,0,91,182,274,366],columns=['days'])
df['base_year']=datetime.date(1960,1,1)

Answer 1

回想起来，MaxU的回答更好。以下内容可能对旧 Pandas 版本有用。

有几种方法可以做到这一点。一种是使用 datetime.timedelta 和列表理解：

from datetime import timedelta
import pandas as pd

>>> [pd.to_datetime('01/01/1960') + timedelta(d) for d in [-730,-640,-549,457,-365,275,-184,-92,0,91,182,274,366]]
[Timestamp('1958-01-01 00:00:00'),
 Timestamp('1958-04-01 00:00:00'),
 Timestamp('1958-07-01 00:00:00'),
 Timestamp('1961-04-02 00:00:00'),
 Timestamp('1959-01-01 00:00:00'),
 Timestamp('1960-10-02 00:00:00'),
 Timestamp('1959-07-01 00:00:00'),
 Timestamp('1959-10-01 00:00:00'),
 Timestamp('1960-01-01 00:00:00'),
 Timestamp('1960-04-01 00:00:00'),
 Timestamp('1960-07-01 00:00:00'),
 Timestamp('1960-10-01 00:00:00'),
 Timestamp('1961-01-01 00:00:00')]

所以你可以使用

>>> DataFrame([pd.to_datetime('01/01/1960') + timedelta(d) for d in [-730,-640,-549,457,-365,275,-184,-92,0,91,182,274,366]],columns=['days'])
    days
0   1958-01-01
1   1958-04-01
2   1958-07-01
3   1961-04-02
4   1959-01-01
5   1960-10-02
6   1959-07-01
7   1959-10-01
8   1960-01-01
9   1960-04-01
10  1960-07-01
11  1960-10-01
12  1961-01-01

Answer 2

您可以使用相对较新的功能（在 Pandas 0.20.0 中添加）- origin of pd.to_datetime():

In [44]: df['date'] = pd.to_datetime(df['days'], origin='1960-01-01', unit='D')

In [45]: df
Out[45]:
    days       date
0   -730 1958-01-01
1   -640 1958-04-01
2   -549 1958-07-01
3    457 1961-04-02
4   -365 1959-01-01
5    275 1960-10-02
6   -184 1959-07-01
7    -92 1959-10-01
8      0 1960-01-01
9     91 1960-04-01
10   182 1960-07-01
11   274 1960-10-01
12   366 1961-01-01

来自docs：

origin : scalar, default is ‘unix’

Define the reference date. The numeric values would be parsed as number of units (defined by unit) since this reference date.

If ‘unix’ (or POSIX) time; origin is set to 1970-01-01. If ‘julian’, unit must be ‘D’, and origin is set to beginning of Julian Calendar.

Julian day number 0 is assigned to the day starting at noon on January

1, 4713 BC. If Timestamp convertible, origin is set to Timestamp identified by origin.

将天数 Int64 转换为日期

Convert Days Int64 to Date

python

datetime

date

timedelta

pandas