I need to multiply the values of a column by 2.2 but only if the values are less than 30. Any help would be much appreciated
Here is what I tried. I know it is super wrong but I have no idea where to go with this. I am new to python, so forgive the really dumb question.
Values less than 30 are in kg and need to be recalculated into pounds.
df['Weight']=np.where(df['Weight'] > 30, df['Weight']*2.2)
Given this dataframe for example:
df = pd.DataFrame({"weight": [10, 20, 30, 40, 50]})
weight
0 10
1 20
2 30
3 40
4 50
You can use .loc like this:
df.loc[df["weight"] < 30, "weight"] = df["weight"] * 2.2
weight
0 22
1 44
2 30
3 40
4 50
You can read more about selecting data here.
You can also use DataFrame.where (not numpy.where):
df["weight"] = df.where(df["weight"] >= 30, df["weight"] * 2.2, axis=0)
weight
0 22
1 44
2 30
3 40
4 50
Or DataFrame.mask:
df["weight"] = df.mask(df["weight"] < 30, df["weight"] * 2.2, axis=0)
weight
0 22
1 44
2 30
3 40
4 50