Pandas Series: value_counts() function
Series containing counts of unique values in Pandas
The value_counts() function is used to get a Series containing counts of unique values.
The resulting object will be in descending order so that the first element is the most frequently-occurring element. Excludes NA values by default.
Syntax:
Series.value_counts(self, normalize=False, sort=True, ascending=False, bins=None, dropna=True)
Parameters:
Name | Description | Type/Default Value | Required / Optional |
---|---|---|---|
normalize | If True then the object returned will contain the relative frequencies of the unique values. | boolean Default Value: False |
Required |
sort | Sort by frequencies. | boolean Default Value: True |
Required |
ascending | Sort in ascending order. | boolean Default Value: False |
Required |
bins | IRather than count values, group them into half-open bins, a convenience for pd.cut, only works with numeric data. | integer | Optional |
dropna | Don’t include counts of NaN. | boolean Default Value: True |
Required |
Returns: Series
Example:
Python-Pandas Code:
import numpy as np
import pandas as pd
index = pd.Index([2, 2, 5, 3, 4, np.nan])
index.value_counts()
Output:
2.0 2 4.0 1 3.0 1 5.0 1 dtype: int64
Example - With normalize set to True, returns the relative frequency by dividing all values by the sum of values:
Python-Pandas Code:
import numpy as np
import pandas as pd
s = pd.Series([2, 2, 5, 3, 4, np.nan])
s.value_counts(normalize=True)
Output:
2.0 0.4 4.0 0.2 3.0 0.2 5.0 0.2 dtype: float64
Example - bins:
Bins can be useful for going from a continuous variable to a categorical variable; instead of counting unique apparitions of values, divide the index in the specified number of half-open bins.
Python-Pandas Code:
import numpy as np
import pandas as pd
s = pd.Series([2, 2, 5, 3, 4, np.nan])
s.value_counts(bins=3)
Output:
(1.9960000000000002, 3.0] 3 (4.0, 5.0] 1 (3.0, 4.0] 1 dtype: int64
Example - dropna:
With dropna set to False we can also see NaN index values.
Python-Pandas Code:
import numpy as np
import pandas as pd
s = pd.Series([2, 2, 5, 3, 4, np.nan])
s.value_counts(dropna=False)
Output:
2.0 2 NaN 1 4.0 1 3.0 1 5.0 1 dtype: int64
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