How to impute values in a column and overwrite existing values - python-3.x

Question

Im trying to learn machine learning and i need to fill in the missing values for the cleaning stage of the workflow. i have 13 columns and need to impute the values for 8 of them. One column is called Dependents and i want to fill in the blanks with the word missing and change the cells that do contain data as follows: 1 to one, two to 2, 3 to three and 3+ to threePlus.
Im running the program in Anaconda and the name of the dataframe is train
train.columns
this gives me
Index(['Loan_ID', 'Gender', 'Married', 'Dependents', 'Education',
'Self_Employed', 'ApplicantIncome', 'CoapplicantIncome', 'LoanAmount',
'Loan_Amount_Term', 'Credit_History', 'Property_Area', 'Loan_Status'],
dtype='object')
next
print("Dependents")
print(train['Dependents'].unique())
this gives me
Dependents
['0' '1' '2' '3+' nan]
now i try imputing values as stated
def impute_dependent():
my_dict={'1':'one','2':'two','3':'three','3+':'threePlus'};
return train.Dependents.map(my_dict).fillna('missing')
def convert_data(dataset):
temp_data = dataset.copy()
temp_data['Dependents'] = temp_data[['Dependents']].apply(impute_dependent,axis=1)
return temp_data
this gives the error
TypeError Traceback (most recent call last)
<ipython-input-46-ccb1a5ea7edd> in <module>()
4 return temp_data
5
----> 6 train_dataset = convert_data(train)
7 #test_dataset = convert_data(test)
<ipython-input-46-ccb1a5ea7edd> in convert_data(dataset)
1 def convert_data(dataset):
2 temp_data = dataset.copy()
----> 3 temp_data['Dependents'] =
temp_data[['Dependents']].apply(impute_dependent,axis=1)
4 return temp_data
5
D:\Anaconda2\lib\site-packages\pandas\core\frame.py in apply(self, func,
axis, broadcast, raw, reduce, result_type, args, **kwds)
6002 args=args,
6003 kwds=kwds)
-> 6004 return op.get_result()
6005
6006 def applymap(self, func):
D:\Anaconda2\lib\site-packages\pandas\core\apply.py in get_result(self)
140 return self.apply_raw()
141
--> 142 return self.apply_standard()
143
144 def apply_empty_result(self):
D:\Anaconda2\lib\site-packages\pandas\core\apply.py in apply_standard(self)
246
247 # compute the result using the series generator
--> 248 self.apply_series_generator()
249
250 # wrap results
D:\Anaconda2\lib\site-packages\pandas\core\apply.py in
apply_series_generator(self)
275 try:
276 for i, v in enumerate(series_gen):
--> 277 results[i] = self.f(v)
278 keys.append(v.name)
279 except Exception as e:
TypeError: ('impute_dependent() takes 0 positional arguments but 1 was
given', 'occurred at index 0')
i expected one, two , three and threePlus to replace the existing values and missing to fill in the blanks

Answer 1

Would this do?
my_dict = {'1':'one','2':'two','3':'three','3+':'threePlus', np.nan: 'missing'}
def convert_data(dataset):
temp_data = dataset.copy()
temp_data.Dependents = temp_data.Dependents.map(my_dict)
return temp_data
As a side note, part of your problem might be the use of apply: essentially apply passes data through a function and puts in what comes out. I might be wrong but I think your function needs to take the input given by apply, eg:
def impute_dependent(dep):
my_dict = {'1':'one','2':'two','3':'three','3+':'threePlus', np.nan: 'missing'}
return my_dict[dep]
df.dependents = df.dependents.apply(impute_dependents)
This way, for every value in df.dependents, apply will take that value and give it to impute_dependents as an argument, then take the returned value as output. As is, when I trial your code I get an error because impute_dependent takes no arguments.