Pandas 数据框：两列相乘

Question

I am trying to multiply two columns (ActualSalary * FTE) within the dataframe (OPR) to create a new column (FTESalary), but somehow it has stopped at row 21357, I don't understand what went wrong or how to fix it. The two columns came from importing a csv file using the line: OPR = pd.read_csv('OPR.csv', encoding='latin1')

[In] OPR
[out]
ActualSalary    FTE
44600           1
58,000.00       1
70,000.00       1
17550           1
34693           1
15674           0.4

[In] OPR["FTESalary"] = OPR["ActualSalary"].str.replace(",", "").astype("float")*OPR["FTE"]
[In] OPR
[out]
ActualSalary    FTE FTESalary
44600           1   44600
58,000.00       1   58000
70,000.00       1   70000
17550           1   NaN
34693           1   NaN
15674           0.4 NaN

I am not expecting any NULL values as an output at all, I am really struggling with this. I would really appreciate the help. Many thanks in advance! (I am new to both coding and here, please let me know via message if I have made mistakes or can improve the way I post questions here)

Sharing the data @oppresiveslayer

[In] OPR[0:6].to_dict()
[out]
{'ActualSalary': {0: '44600',
1: '58,000.00',
2: '70,000.00',
3: '39,780.00',
4: '0.00',
5: '78,850.00'},
 'FTE': {0: 1.0, 1: 1.0, 2: 1.0, 3: 1.0, 4: 1.0, 5: 1.0}}

For more information on the two columns @charlesreid1

[in] OPR['ActualSalary'].astype
[out]
Name: ActualSalary, Length: 21567, dtype: object>

[in] OPR['FTE'].astype
[out]
Name: FTE, Length: 21567, dtype: float64>

The version I am using: python: 3.7.3, pandas: 0.25.1 on jupyter Notebook 6.0.0

Answer 1

I believe that your ActualSalary column is a mix of strings and integers. That is the only way I've been able to recreate your error:

df = pd.DataFrame(
    {'ActualSalary': ['44600', '58,000.00', '70,000.00', 17550, 34693, 15674],
     'FTE': [1, 1, 1, 1, 1, 0.4]})

>>> df['ActualSalary'].str.replace(',', '').astype(float) * df['FTE']
0    44600.0
1    58000.0
2    70000.0
3        NaN
4        NaN
5        NaN
dtype: float64

The issue arises when you try to remove the commas:

>>> df['ActualSalary'].str.replace(',', '')
0       44600
1    58000.00
2    70000.00
3         NaN
4         NaN
5         NaN
Name: ActualSalary, dtype: object

First convert them to strings, before converting back to floats.

fte_salary = (
    df['ActualSalary'].astype(str).str.replace(',', '')  # Remove commas in string, e.g. '55,000.00' -> '55000.00'
    .astype(float)  # Convert string column to floats.
    .mul(df['FTE'])  # Multiply by new salary column by Full-Time-Equivalent (FTE) column.
)
>>> df.assign(FTESalary=fte_salary)  # Assign new column to dataframe.
      ActualSalary  FTE  FTESalary
    0        44600  1.0    44600.0
    1    58,000.00  1.0    58000.0
    2    70,000.00  1.0    70000.0
    3        17550  1.0    17550.0
    4        34693  1.0    34693.0
    5        15674  0.4     6269.6

Answer 2

This should work:

OTR['FTESalary'] = OTR.apply(lambda x: pd.to_numeric(x['ActualSalary'].replace(",", ""), errors='coerce') * x['FTE'], axis=1)

output

  ActualSalary  FTE  FTESalary
0        44600  1.0    44600.0
1    58,000.00  1.0    58000.0
2    70,000.00  1.0    70000.0
3        17550  1.0    17550.0
4        34693  1.0    34693.0
5        15674  0.4     6269.6

ok, i think you need to do this:

OTR['FTESalary'] = OTR.reset_index().apply(lambda x: pd.to_numeric(x['ActualSalary'].replace(",", ""), errors='coerce') * x['FTE'], axis=1).to_numpy().tolist() 

Answer 3

I was able to do it in a couple steps, but with list comprehension which might be less readable for a beginner. It makes an intermediate column, which does the float conversion, since your ActualSalary column is full of strings at the start.

OPR["X"] = [float(x.replace(",","")) for x in OPR["ActualSalary"]]
OPR["FTESalary"] = OPR["X"]*OPR["FTE"]