累加和数据框的条件计数-遍历列 [英] Conditional count of cumulative sum Dataframe - Loop through columns
问题描述
我正在尝试根据每个值的符号来计算数据帧内带有重置的累积总和.想法是每列分别进行相同的练习.
Im trying to compute a cumulative sum with a reset within a dataframe, based on the sign of each values. The idea is to the same exercise for each column separately.
例如,假设我具有以下数据框:
For example, let's assume I have the following dataframe:
df = pd.DataFrame({'A': [1,1,1,-1,-1,1,1,1,1,-1,-1,-1],'B':[1,1,-1,-1,-1,1,1,1,-1,-1,-1,1]},index=[0, 1, 2, 3,4,5,6,7,8,9,10,11])
对于每一列,我要计算累积和,直到找到符号变化为止.在这种情况下,总和应重置为1.对于上面的示例,我期望得到以下结果:
For each column, I want to compute the cumulative sum until I find a change in sign; in which case, the sum should be reset to 1. For the example above, I am expecting the following result:
df1=pd.DataFrame({'A_cumcount':[1,2,3,1,2,1,2,3,4,1,2,3],'B_cumcount':[1,2,1,2,3,1,2,3,1,2,3,4],index=[0,1,2,3,4,5,6,7,8,9,10,11]})
此处已讨论过类似的问题:熊猫:有条件的滚动计数
Similar issue has been discussed here: Pandas: conditional rolling count
我尝试了以下代码:
nb_col=len(df.columns) #number of columns in dataframe
for i in range(0,int(nb_col)): #Loop through the number of columns in the dataframe
name=df.columns[i] #read the column name
name=name+'_cumcount'
#add column for the calculation
df=df.reindex(columns=np.append(df.columns.values, [name]))
df=df[df.columns[nb_col+i]]=df.groupby((df[df.columns[i]] != df[df.columns[i]].shift(1)).cumsum()).cumcount()+1
我的问题是,有没有办法避免这种for循环?因此,我可以避免每次都附加一个新列,并使计算速度更快.谢谢
My question is, is there a way to avoid this for loop? So I can avoid appending a new column each time and make the computation faster. Thank you
收到答复(一切正常):
来自@nixon
df.apply(lambda x: x.groupby(x.diff().ne(0).cumsum()).cumcount()+1).add_suffix('_cumcount')
Answers received (all working fine):
From @nixon
df.apply(lambda x: x.groupby(x.diff().ne(0).cumsum()).cumcount()+1).add_suffix('_cumcount')
来自@jezrael
df1 = (df.apply(lambda x: x.groupby((x != x.shift()).cumsum()).cumcount() + 1).add_suffix('_cumcount'))
From @jezrael
df1 = (df.apply(lambda x: x.groupby((x != x.shift()).cumsum()).cumcount() + 1).add_suffix('_cumcount'))
来自@斯科特波士顿(Scott Boston):
From @Scott Boston:
df.apply(lambda x: x.groupby(x.diff().bfill().ne(0).cumsum()).cumcount() + 1)
推荐答案
我认为在熊猫中需要循环,例如通过apply
:
I think in pandas need loop, e.g. by apply
:
df1 = (df.apply(lambda x: x.groupby((x != x.shift()).cumsum()).cumcount() + 1)
.add_suffix('_cumcount'))
print (df1)
A_cumcount B_cumcount
0 1 1
1 2 2
2 3 1
3 1 2
4 2 3
5 1 1
6 2 2
7 3 3
8 4 1
9 1 2
10 2 3
11 3 1
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