CODEWITHSUNDEEP
pythonpython-3.xpandas
Sano babu
Sano babu

Reputation: 105

Python Pandas, New column with minimum value of previous rows

I am trying to create a new column where the value will be the minimum value of all previous rows from existing columns.

For example: Here is my data frame:

    A  nbr
0  AA    4
1  AB    5
2  AC    2
3  AD    5
4  AE    3
5  AF    6
6  AG    1
7  AH    4

I am trying to add a new column 'nbr_min' using the column nbr.

So the first row for nbr_min will be 4, since this is he first row and the minimum of 4 is 4.
Second row will be the minimum of 4 and 5, which is 4. Third row will be the minimum of 4,5,and 2, which is 2. And so on... The final result should look like this.
enter image description here

I am having hard time doing this in python (with pandas). Any help will be appreciated. I am very close to conclude that this can not be done with python. So solution in any other way is also welcome.

.

Upvotes: 0

Views: 636

Answers (1)

anky
anky

Reputation: 75150

Use series.cummin():

df['nbr_min']=df.nbr.expanding().min()

Or:

df['nbr_min']=df.nbr.cummin()
print(df)

    A  nbr  nbr_min
0  AA    4        4
1  AB    5        4
2  AC    2        2
3  AD    5        2
4  AE    3        2
5  AF    6        2
6  AG    1        1
7  AH    4        1

Upvotes: 1

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