[英]counting unique values using .groupby in pandas dataframe
I have a dataframe and I when I run my code it returns all Nan's instead of returning the counted value.我有一个 dataframe,当我运行我的代码时,它返回所有 Nan 而不是返回计数值。 I'm sure it's something simple but I can't figure it out.我确定这很简单,但我无法弄清楚。 I'm trying to get a unique number of species in each location.我试图在每个位置获得唯一数量的物种。 I'd like the new column to output a count of species [2,2,1,1,2,2,1,1]我想在 output 的新专栏中列出物种 [2,2,1,1,2,2,1,1]
import pandas as pd
df = pd.DataFrame({
'ID': [1, 2, 3, 4, 5, 6, 7, 8],
'location': ['A', 'A', 'C', 'C', 'E', 'E', 'E', 'E'],
'Species': ['Cat', 'Cat', 'Dog', 'Cat', 'Cat', 'Cat', 'Dog', 'Bird'],
'Count': [2,2,2,2,4,4,4,4]
})
def abundance(data):
data["Abundance"] = data[data.Species.notnull()].groupby('location')['Species'].unique()
abundance(df)
print(df)
````````````````````
ID location Species Count Abundance
0 1 A Cat 2 NaN
1 2 A Cat 2 NaN
2 3 C Dog 2 NaN
3 4 C Cat 2 NaN
4 5 E Cat 4 NaN
5 6 E Cat 4 NaN
6 7 E Dog 4 NaN
7 8 E Bird 4 NaN
I believe you want count of each pair location, Species
.我相信您想要计数每对location, Species
。 And also, to assign groupby
output back to the original dataframe, we usually use transform
:而且,为了将groupby
output 分配回原来的 dataframe,我们通常使用transform
:
df['Abundance'] = df.groupby(['location','Species']).Species.transform('size')
Output: Output:
ID location Species Count Abundance
0 1 A Cat 2 2
1 2 A Cat 2 2
2 3 C Dog 2 1
3 4 C Cat 2 1
4 5 E Cat 4 2
5 6 E Cat 4 2
6 7 E Dog 4 1
7 8 E Bird 4 1
df.groupby(['location','Species']).Species.value_counts().to_frame('Abundance')
Abundance
location Species Species
A Cat Cat 2
C Cat Cat 1
Dog Dog 1
E Bird Bird 1
Cat Cat 2
Dog Dog 1
I believe you should try grouping the data frame using the columns you want to have in the output,我相信您应该尝试使用 output 中的列对数据框进行分组,
>>> df[df.Species.notnull()].groupby(['location','Species']).count()
ID Count
location Species
A Cat 2 2
C Cat 1 1
Dog 1 1
E Bird 1 1
Cat 2 2
Dog 1 1
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