pandas 数据框上的累积和函数 [英] Cumulative Sum Function on Pandas Data Frame

问题描述

鉴于一系列的期末金额，我试图获取一个正在运行的"累计金额.

I am attempting to capture a "running" cumulative sum given a series of period amounts.

查看示例:

df = df[1:4].cumsum() # this doesn't return the desired result

推荐答案

您正在寻找axis参数.许多Pandas函数都使用此参数来跨列或跨行应用操作.使用axis=0逐行应用，使用axis=1逐列应用.该操作实际上是遍历列，因此您需要axis=1.

You're looking for the axis parameter. Many Pandas functions take this argument to apply an operation across the columns or across the rows. Use axis=0 to apply row-wise and axis=1 to apply column-wise. This operation is actually traversing the columns, so you want axis=1.

df.cumsum(axis=1)本身可用于您的示例以生成输出表.

df.cumsum(axis=1) by itself works on your example to produce the output table.

In [3]: df.cumsum(axis=1)
Out[3]:
      1   2   3   4
10   16  30  41  61
51   13  29  40  50
13   11  30  45  61
321  12  27  37  52

不过，我怀疑您有兴趣将列限制为特定范围.为此，您可以将.loc与列标签(我的字符串)一起使用.

I suspect you're interested in restricting to a specific range of columns, though. To do that, you can use .loc with the column labels (strings in mine).

In [4]: df.loc[:, '2':'3'].cumsum(axis=1)
Out[4]:
      2   3
10   14  25
51   16  27
13   19  34
321  15  25

.loc基于标签，并且包含边界.如果您想了解有关在Pandas中建立索引的更多信息，请查看 docs

.loc is label-based and is inclusive of the bounds. If you want to find out more about indexing in Pandas, check the docs.

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