CODEWITHSUNDEEP
pythonpandas
Struggling brat
Struggling brat

Reputation: 37

How to fill n rows based on a past value in pandas

Following is my dataset:

Name  Rate   Stock   
AB    32.8    0         
CD    56.7   100     
EF    34.7    0
GH    33.1    0      
IJ    44.5   100      
KL    33.6    0

I want to add another column Discount that is 0.95 * Rate. However, it can only use Rate with Stock = 100. It should keep reiterating the Discount value until it finds the next Stock = 100

Here's my desired outcome:

Name   Rate   Stock   Discount 
AB     32.8    0         
CD     56.7   100       53.87
EF     34.7    0        53.87
GH     33.1    0        53.87
IJ     44.5   100       42.28
KL     33.6    0        42.28

Little help will be appreciated! Thanks

Upvotes: 0

Views: 131

Answers (2)

Chris
Chris

Reputation: 29742

One way using boolean indexing with ffill:

df["Discount"] = df["Rate"][df["Stock"].eq(100)] * 0.95
df["Discount"] = df["Discount"].ffill().fillna("")
print(df)

Output:

   Rate  Stock Discount
0  32.8      0         
1  56.7    100   53.865
2  34.7      0   53.865
3  33.1      0   53.865
4  44.5    100   42.275
5  33.6      0   42.275

Upvotes: 2

Corralien
Corralien

Reputation: 120399

You can try:

df['Discount'] = df["Rate"][df["Stock"].eq(100)].mul(0.95) \
                                       .reindex(df.index).ffill()

>>> df
  Name  Rate  Stock  Discount
0   AB  32.8      0       NaN
1   CD  56.7    100    53.865
2   EF  34.7      0    53.865
3   GH  33.1      0    53.865
4   IJ  44.5    100    42.275
5   KL  33.6      0    42.275

Upvotes: 1

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