Python loop over values in dataframe and change to binary values

Question

I have a series y in Python with values Accepted and Rejected. I want to create a new dataframe with value 1 for Accepted and 0 for Rejected.

I'm trying to loop through the values of y and write to a new df dummy. My progress so far is

dummy=pd.DataFrame()
i=0

for i in range(0,len(y)):
    if y[i]=='Approved': 
        dummy[i:]==1
    else: 
        dummy[i:]==0

but I got a feeling that I'm off track. Can anyone help me out?

The series y looks like this:

   y
Accepted
Rejected
Accepted
Accepted
Accepted

The desired output should be something like

jezrael · Accepted Answer · 2019-08-12 09:22:47Z

3

Here loop is not necessary, because slow. Better is convert boolean mask to True/False to 0,1 by converting to integers or use numpy.where:

df['dummy'] =  (df['y']=='Approved').astype(int)

df['dummy'] =  np.where(df['y']=='Approved', 1, 0)

Your solution should be changed (loopy slow solution):

print (df)

0  Accepted
1  Rejected
2  Accepted
3  Accepted
4  Accepted

out = []
for i in range(0,len(df)):
    if df.loc[i, 'y']=='Accepted': 
        out.append(1)
    else: 
        out.append(0)

print (out)
[1, 0, 1, 1, 1]

df['dummy'] = out
print (df)
          y  dummy
0  Accepted      1
1  Rejected      0
2  Accepted      1
3  Accepted      1
4  Accepted      1

edited Aug 12, 2019 at 9:22

answered Aug 12, 2019 at 9:14

jezrael

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1 Comment

jezrael Over a year ago

@Artem - yes, added to answer.

kederrac · Accepted Answer · 2019-08-12 09:27:33Z

1

you can use:

df['dummy'] = df.y.apply(lambda x:  1 if  x == 'Accepted' else 0)

if you want to use a for loop:

new_dummy_data = []

for value in df.y.values:
    if value == 'Accepted':
        new_dummy_data.append(1)
    else:
        new_dummy_data.append(0)

df['dummy'] = new_dummy_data

edited Aug 12, 2019 at 9:27

answered Aug 12, 2019 at 9:20

kederrac

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2 Comments

jezrael Over a year ago

apply is loop under the hood ;)

kederrac Over a year ago

yep, but not in the way the OP wants, I mean a visible for loop

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