if statement and for loop
I am stuck with the following code, I have a column in which I want to divide by 2 if the number is above 10 and run this for all the rows. I have tried this code but it gives the error of the series is ambiguous:
if df[x] > 10: df[x]/2 else: df[x]
I suppose that I need a for loop in combination with the if statement. However I could not make it running, anyone has some ideas?
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Answer
The easiest approach, I think, is to use boolean indexing. For example:
df = pd.DataFrame( # create dataframe
20*np.random.rand(6, 4),
columns=list("ABCD"))
print(df) # print df
df[df>10]/=2 # divide entries over 10 by 2
print(df) # print df
Result:
A B C D
0 1.245686 1.443671 17.423559 17.617235
1 13.834285 10.482565 2.213459 9.581361
2 0.290626 14.082919 0.224327 11.033058
3 5.113568 5.305690 19.453723 3.260354
4 14.679005 8.761523 2.417432 4.843426
5 15.990754 12.421538 4.872804 5.577625
A B C D
0 1.245686 1.443671 8.711780 8.808617
1 6.917143 5.241283 2.213459 9.581361
2 0.290626 7.041459 0.224327 5.516529
3 5.113568 5.305690 9.726862 3.260354
4 7.339503 8.761523 2.417432 4.843426
5 7.995377 6.210769 4.872804 5.577625