如何计算包括零出现在内的分类值? [英] how to count categorical values including zero occurrence?
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问题描述
我想按月计算代码数量.这是我的示例数据框.
I want to count number of code by month. This is my example dataframe.
id month code
0 sally 0 s_A
1 sally 0 s_B
2 sally 0 s_C
3 sally 0 s_D
4 sally 0 s_E
5 sally 0 s_A
6 sally 0 s_A
7 sally 0 s_B
8 sally 0 s_C
9 sally 0 s_A
我使用 count() 转换为这个系列.
I transformed to this Series using count().
df.groupby(['id', 'code', 'month']).month.count()
id code month count
sally s_A 0 12
1 10
2 3
7 15
但是,我想包括零出现,就像这样.
But, I want to include zero occurrence, like this.
id code month count
sally s_A 0 12
1 10
2 3
3 0
4 0
5 0
6 0
7 15
8 0
9 0
10 0
11 0
推荐答案
您可以使用 reindex
使用新的 Multindex
创建 from_product
:
You can use reindex
with new Multindex
created from_product
:
df = pd.DataFrame({
'month': [0, 0, 0, 0, 1, 1, 1, 2, 2, 7],
'code': ['s_A', 's_A', 's_A', 's_A', 's_A', 's_A', 's_A', 's_B', 's_B', 's_B'],
'id': ['sally1','sally1','sally1','sally','sally','sally','sally','sally','sally','sally']})
print (df)
code id month
0 s_A sally1 0
1 s_A sally1 0
2 s_A sally1 0
3 s_A sally 0
4 s_A sally 1
5 s_A sally 1
6 s_A sally 1
7 s_B sally 2
8 s_B sally 2
9 s_B sally 7
<小时>
df = df.groupby(['id', 'code', 'month']).size()
n = ['id','code','month']
mux = pd.MultiIndex.from_product([df.index.levels[0],df.index.levels[1], range(13)], names=n)
df = df.reindex(mux, fill_value=0)
print (df)
id code month
sally s_A 0 1
1 3
2 0
3 0
4 0
5 0
6 0
7 0
8 0
9 0
10 0
11 0
12 0
s_B 0 0
1 0
2 2
3 0
...
...
旧解决方案:
reindex
使用 unstack
和 stack
,但是需要一些数据清理:
reindex
with unstack
and stack
, but then need some data cleaning:
df = df.groupby(['id', 'code', 'month']).size() \
.to_frame('count') \
.unstack([0,1], fill_value=0) \
.reindex(range(13), fill_value=0) \
.stack([1,2], dropna=False) \
.fillna(0) \
.astype(int) \
.swaplevel(0,2) \
.sort_index()
print (df)
count
code id month
s_A sally 0 1
1 3
2 0
3 0
4 0
5 0
6 0
7 0
8 0
9 0
10 0
11 0
12 0
sally1 0 3
1 0
2 0
3 0
4 0
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