How to properly apply a lambda function into a pandas data frame column

Question

I have a pandas data frame, sample, with one of the columns called PR to which am applying a lambda function as follows:

sample[\'P         


        

Answer 1

You need to add else in your lambda function. Because you are telling what to do in case your condition(here x < 90) is met, but you are not telling what to do in case the condition is not met.

sample['PR'] = sample['PR'].apply(lambda x: 'NaN' if x < 90 else x)