pandas :垫系列在顶部或底部 [英] Pandas: pad series on top or bottom
问题描述
对于我来说,这实在是不平凡的,所以我想检查一下其他人是否对此有一个简单的解决方案:
This turned out to be non-trivial for me so I wanted to check if others have a simple solution for this:
假设我有一个任意数量的(例如3)pd.Series
:看起来像:
Suppose I have an arbitrary number (say 3) of pd.Series
: which look like:
first = pd.Series(range(5))
second = pd.Series(range(7))
third = pd.Series(range(6))
我想让它们都具有相同的长度(7-这是最大的长度),并在顶部(可选地在底部)上用np.nan
填充较短的那些,以便使第一个看起来像:
I'd like to make them all of the same length (7 -- which is the largest length) and pad the shorter ones with np.nan
s either at the top (optionally at the bottom) so that first looks like:
nan
nan
0
1
2
3
4
以此类推.
推荐答案
You could use reindex
to give each Series a new index. If the new index contains labels which are not in the original series' index, then a NaN
value is filled in (unless a different fill_value
is specified):
In [15]: first.reindex(range(7))
Out[15]:
0 0.0
1 1.0
2 2.0
3 3.0
4 4.0
5 NaN
6 NaN
dtype: float64
您可以通过选择重新索引标签来控制NaN的放置:
You can control the placement of the NaNs by your choice of reindexing labels:
In [19]: first.reindex(range(-2,5))
Out[19]:
-2 NaN
-1 NaN
0 0.0
1 1.0
2 2.0
3 3.0
4 4.0
dtype: float64
请注意,包含NaN
会强制将first
的dtype从整数dtype提升为浮点dtype,因为NaN
都是浮点数(因此,整数dtype系列不能包含NaN
s).
Note that the inclusion of NaN
s forces the dtype of first
to be promoted from an integer dtype to a floating-point dtype since NaN
s are floats (and hence Series of integer dtype can not contain NaN
s).
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