How can I change all negative values in a specific column of a pandas dataframe to Null/NaN?

Question

I have what I believe to be some anomalies in my dataset so I want to change all negative values in a specific column of a pandas dataframe to Null/NaN

This is the code I have so far:

df_1[df_1['Column D']<0] = np.nan

But what it is doing is changing all the values in the row that have a negative in column D to NaN when I only need the negative values in Column D changed

I have also played around using df.loc, df.replace and df.mask but couldn't find a way that worked.

Answer 1

two options:

a)

df_1.loc[df_1['Column D'] < 0, 'Column D'] = np.nan

b)

df_1['Column D'] = df_1['Column D'].mask(df_1['Column D'] < 0, np.nan)

they both should work correctly, not sure which one is faster, it's a trivial question , you have chance to test them it would be cool to have it on file.