Pandas Dataframe 从列中减去浮点值

Question

Is there a way to subtract a constant value from the whole column?

If my dataframe is

I want to subtract 2.5 from column 1 so that it appears as

Also, is it possible to convert Date+Time into minutes?

Thank you!

Answer 1

If df is your dataframe, simply use

df.Distance += 2.5

for adding a constant, or

df.Distance -= 2.5

for subtracting it.

(I'm not sure which one of them you want to do.)

Answer 2

using .apply is always a fast way to handle something like this

#data.csv is you data
import pandas as pd
df = pd.DataFrame.read_csv('data.csv')

#you want to perform this operation on column 1 that has a label 'A'
#make a function
def col_subtract(row):
    row['A'] = row['A'] - 2.5
    return row

#apply the function to the dataframe
df = df.apply(col_subtract, axis=1)

doc

note: you could also just pass it a lambda function, I just felt it was cleaner to make a formal user defined function with a name to emphasize what you're doing.