在 pandas 中绕一列 [英] round a single column in pandas

问题描述

是否可以在不影响数据帧其余部分的情况下在熊猫中舍入单个列?

Is there a way to round a single column in pandas without affecting the rest of the dataframe?

 df:
      item  value1  value2
    0    a    1.12     1.3
    1    a    1.50     2.5
    2    a    0.10     0.0
    3    b    3.30    -1.0
    4    b    4.80    -1.0

df.value1.apply(np.round) 给

df.value1.apply(np.round) gives

0    1
1    2
2    0
3    3
4    5
5    5

使数据看起来像这样的正确方法是什么?

What is the correct way to make data look like this:

  item  value1  value2
0    a       1     1.3
1    a       2     2.5
2    a       0     0.0
3    b       3    -1.0
4    b       5    -1.0
5    c       5     5.0

推荐答案

您非常亲密. 您已将回合应用于df.value1给定的一系列值. 因此，返回类型为Series. 您需要将该系列分配回数据框(或具有相同索引的另一个数据框).

You are very close. You applied the round to the series of values given by df.value1. The return type is thus a Series. You need to assign that series back to the dataframe (or another dataframe with the same Index).

此外，还有一个 pandas.Series.round 方法，基本上是pandas.Series.apply(np.round)的简写.

Also, there is a pandas.Series.round method which is basically a short hand for pandas.Series.apply(np.round).

In[2]: 
    df.value1 = df.value1.round()
    print df

Out[2]:
    item  value1  value2
    0    a       1     1.3
    1    a       2     2.5
    2    a       0     0.0
    3    b       3    -1.0
    4    b       5    -1.0

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