Dataframe column value using max() function

Question

I am trying to create a column called "Threshold" where the values are determined by calculation df['column']/30**0.5 , but I want this column to have a minimum value of 0.2. So if the calculation is below 0.2, I want the column value to be 0.2.

For example: df['column2'] = (df['column']/30)**0.5 or 0.2 (which ever number is larger).

This is what I have currently:

df['Historical_MovingAverage_15'] = df['Historical_Average'].rolling(window=15).mean()
df['Threshold'] = max((((df['Historical_MovingAverage_15'])/30)**0.5), 0.2)

It gives me this error:

ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

jezrael · Accepted Answer · 2020-04-30 04:16:13Z

4

Use numpy.maximum:

df['Threshold'] = np.maximum((((df['Historical_MovingAverage_15'])/30)**0.5), 0.2)

Or Series.clip with lower parameter:

df['Threshold'] = (((df['Historical_MovingAverage_15'])/30)**0.5).clip(lower=0.2)

Sample:

df = pd.DataFrame({'Historical_MovingAverage_15':[.21,2,3]})
df['Threshold'] = np.maximum((((df['Historical_MovingAverage_15'])/30)**0.5), 0.2)
print (df)
   Historical_MovingAverage_15  Threshold
0                         0.21   0.200000
1                         2.00   0.258199
2                         3.00   0.316228

Detail:

print ((((df['Historical_MovingAverage_15'])/30)**0.5))
0    0.083666
1    0.258199
2    0.316228
Name: Historical_MovingAverage_15, dtype: float64

answered Apr 30, 2020 at 4:16

jezrael

868k103 gold badges1.4k silver badges1.3k bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

meronpan Over a year ago

Thanks! I decided to use .clip() since I don't need to import another library. Works perfectly.

Thomas Devoogdt Over a year ago

Filtering can also be done with apply: df[df["column"].apply(lambda x: return x >= 0.2)]

Collectives™ on Stack Overflow

Dataframe column value using max() function

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related