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Python Pandas DataFrame.interpolate() function fills values ​​in a DataFrame using interpolation technique NaN.

pandas.DataFrame.interpolate()grammar

DataFrame.interpolate(
    method="linear",
    axis=0,
    limit=None,
    inplace=False,
    limit_direction="forward",
    limit_area=None,
    downcast=None,
    **kwargs
)

parameter

Return Value

If inplaceis , then all values ​​are interpolated Trueusing the given ; otherwise is .methodNaNDataFrameNone

Example code: Use DataFrame.interpolate()the method to interpolate DataFrameall the values ​​inNaN

import pandas as pd

df = pd.DataFrame({'X': [1, 2, 3, None, 3],
                   'Y': [4, None, 8, None, 3]})
print("DataFrame:")
print(df)

filled_df = df.interpolate()

print("Interploated DataFrame:")
print(filled_df)

Output:

DataFrame:
     X    Y
0  1.0  4.0
1  2.0  NaN
2  3.0  8.0
3  NaN  NaN
4  3.0  3.0
Interploated DataFrame:
     X    Y
0  1.0  4.0
1  2.0  6.0
2  3.0  8.0
3  3.0  5.5
4  3.0  3.0

It interpolates all the values linear​​in using the interpolation method .DataFrameNaN

This method is smarter than pandas.DataFrame.fillna() , which replaces DataFrame.all values ​​in with a fixed value NaN.

Example code: DataFrame.interpolate()Method with methodparameters

We can also DataFrame.interpolate()set methodthe parameter value in the function and use different interpolation techniques to interpolate the value DataFrameof in .NaN

import pandas as pd

df = pd.DataFrame({'X': [1, 2, 3, None, 3],
                   'Y': [4, None, 8, None, 3]})
print("DataFrame:")
print(df)

filled_df = df.interpolate(method='polynomial', order=2)

print("Interploated DataFrame:")
print(filled_df)

Output:

DataFrame:
     X    Y
0  1.0  4.0
1  2.0  NaN
2  3.0  8.0
3  NaN  NaN
4  3.0  3.0
Interploated DataFrame:
          X      Y
0  1.000000  4.000
1  2.000000  7.125
2  3.000000  8.000
3  3.368421  6.625
4  3.000000  3.000

This method interpolates DataFrameall the values ​​of in using a second-order polynomial interpolation method.NaN

Here, order=2are polynomialthe keyword arguments to the function.

Example Code: Pandas Method to Interpolate Along the Axis DataFrame.interpolate()Using the Parameteraxisrow

import pandas as pd

df = pd.DataFrame({'X': [1, 2, 3, None, 3],
                   'Y': [4, None, 8, None, 3]})
print("DataFrame:")
print(df)

filled_df = df.interpolate(axis=1)

print("Interploated DataFrame:")
print(filled_df)

Output:

DataFrame:
     X    Y
0  1.0  4.0
1  2.0  NaN
2  3.0  8.0
3  NaN  NaN
4  3.0  3.0
Interploated DataFrame:
     X    Y
0  1.0  4.0
1  2.0  2.0
2  3.0  8.0
3  NaN  NaN
4  3.0  3.0

Here, we set axis=1to interpolate the values ​​along the row axis NaN. At row 2, NaNthe values ​​are replaced by linear interpolation along row 2.

However, in row 4, since both values ​​in row 4 are , the value remains NaNeven after interpolation .NaN

Example code: DataFrame.interpolate()Method with limitparameters

DataFrame.interpolate()The parameter in the method limitlimits NaNthe maximum number of consecutive values ​​that the method will fill.

import pandas as pd

df = pd.DataFrame({'X': [1, 2, 3, None, 3],
                   'Y': [4, None, None, None, 3]})
print("DataFrame:")
print(df)

filled_df = df.interpolate( limit = 1)

print("Interploated DataFrame:")
print(filled_df)

Output:

DataFrame:
     X    Y
0  1.0  4.0
1  2.0  NaN
2  3.0  NaN
3  NaN  NaN
4  3.0  3.0
Interploated DataFrame:
     X     Y
0  1.0  4.00
1  2.0  3.75
2  3.0   NaN
3  3.0   NaN
4  3.0  3.00

Here, when a NaNvalue in a column is filled from top to bottom, the next consecutive NaNvalue in the same column remains unchanged.

Example code: DataFrame.interpolate()Method with limit_directionparameters

DataFrame.interpolate()The parameter in the method limit-directioncontrols the direction along the specific axis in which the values ​​are interpolated.

import pandas as pd

df = pd.DataFrame({'X': [1, 2, 3, None, 3],
                   'Y': [4, None, None, None, 3]})
print("DataFrame:")
print(df)

filled_df = df.interpolate(limit_direction ='backward', limit = 1)

print("Interploated DataFrame:")
print(filled_df)

Output:

DataFrame:
     X    Y
0  1.0  4.0
1  2.0  NaN
2  3.0  NaN
3  NaN  NaN
4  3.0  3.0
Interploated DataFrame:
     X     Y
0  1.0  4.00
1  2.0   NaN
2  3.0   NaN
3  3.0  3.25
4  3.0  3.00

Here, when the in a column NaNis filled from the bottom, the next consecutive NaNvalue in the same column remains unchanged.

DataFrame.interpolate()Interpolate time series data using

import pandas as pd

dates=['April-10', 'April-11', 'April-12', 'April-13']
fruits=['Apple', 'Papaya', 'Banana', 'Mango']
prices=[3, None, 2, 4]

df = pd.DataFrame({'Date':dates ,
                   'Fruit':fruits ,
                   'Price': prices})

print(df)
df.interpolate(inplace=True)

print("Interploated DataFrame:")
print(df)

Output:

       Date   Fruit  Price
0  April-10   Apple    3.0
1  April-11  Papaya    NaN
2  April-12  Banana    2.0
3  April-13   Mango    4.0
Interploated DataFrame:
       Date   Fruit  Price
0  April-10   Apple    3.0
1  April-11  Papaya    2.5
2  April-12  Banana    2.0
3  April-13   Mango    4.0

Because inplace=True, after calling interpolate()the function, the original DataFrameis modified.