CODEWITHSUNDEEP
pythonpandasconditional-statements
Rolf12
Rolf12

Reputation: 771

Python: Multiple conditions questions on pandas columns

I have a question regarding multiple-conditions on pandas columns. I have the following dataframe:

    A   B   C
0   0   9   0
1   1   8   0
2   1   9   0
3   1   5   1
4   1   9   1
5   1   8   1
6   -1  9   0
7   -1  5   -1
8   -1  7   -1

What I am trying to achieve is the following:

1.) If A>0 and B <6 C should become a 1 and keep that until A changes (B could get above 6)

2.) If A<0 and B <6 C should become a -1 and keep that until A changes (B could get above 6)

Any suggestions how to do that without a loop?

I am struggeling with how to "memorize" the status of B having been below 6 for the current A= 1 or A=-1 period.

Thanks for any suggestions

Upvotes: 1

Views: 223

Answers (1)

BENY
BENY

Reputation: 323226

Using np.select create your help column when satisfied your own conditions , then we do groupby with bfill

s1=(df.A>0)&(df.B<6)
s2=(df.A<0)&(df.B<6)
df['v']=np.select([s1,s2],[1,-1])
df.v.replace(0,np.nan).groupby(df.A).ffill().fillna(0).astype(int)
Out[1023]: 
0    0
1    0
2    0
3    1
4    1
5    1
6    0
7   -1
8   -1

Upvotes: 1

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