Pandas Groupby 应用函数计算大于零的值 [英] Pandas Groupby apply function to count values greater than zero

问题描述

Pandas Groupby 应用函数计算大于零的值

Pandas Groupby apply function to count values greater than zero

我以下列方式使用 groupby 和 agg:

I am using groupby and agg in the following manner:

df.groupby('group')['a'].agg({'mean' : np.mean, 'std' : np.std})

并且我还想计算同一列 ['a'] 中高于零的值

and I would like to also count the values above zero in the same column ['a']

以下行按照我的意愿进行计数，

the following line does the count as I want,

sum(x > 0 for x in df['a'])

但是我在申请 groupby 时无法使用它.

but I can't get it work when applying to groupby.

以下示例将 Pandas 计算应用于我尝试过的 groupby:

Following an example for applying a pandas calculation to a groupby I tried:

df.groupby('group')['a'].apply(sum(x > 0 for x in df['a']))

但我收到一条错误消息:AttributeError: 'numpy.int32' 对象没有属性 'module'

but I get an error message: AttributeError: 'numpy.int32' object has no attribute 'module'

有人可以建议如何做到这一点吗?

Can anybody please suggest how this might be done?

推荐答案

来自评论的回答:

 .agg({'pos':lambda ts: (ts > 0).sum()}) # –  behzad.nouri Mar 31 at 0:00 

这是我对未回答问题积压的贡献:)归功于 behzad.nouri

This is my contribution to the backlog of unanswered questions :) Credits to behzad.nouri

2020 年更新在最新的pandas版本中，需要做如下操作:

Update 2020 In the latest pandas version, you need to do the following:

 .agg(pos=lambda ts: (ts > 0).sum()) 

否则会导致如下错误:

SpecificationError: nested renamer is not supported

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