Python Pandas: Convert ".value_counts" output to dataframe
Question:
Hi I want to get the counts of unique values of the dataframe. count_values implements this however I want to use its output somewhere else. How can I convert .count_values output to a pandas dataframe. here is an example code:
import pandas as pd
df = pd.DataFrame({'a':[1, 1, 2, 2, 2]})
value_counts = df['a'].value_counts(dropna=True, sort=True)
print(value_counts)
print(type(value_counts))
output is:
2 3
1 2
Name: a, dtype: int64
<class 'pandas.core.series.Series'>
What I need is a dataframe like this:
unique_values counts
2 3
1 2
Thank you.
Answers:
Use rename_axis for name of column from index and reset_index:
df = df.value_counts().rename_axis('unique_values').reset_index(name='counts')
print (df)
unique_values counts
0 2 3
1 1 2
Or if need one column DataFrame use Series.to_frame:
df = df.value_counts().rename_axis('unique_values').to_frame('counts')
print (df)
counts
unique_values
2 3
1 2
I just run into the same problem, so I provide my thoughts here.
Warning
When you deal with the data structure of Pandas, you have to aware of the return type.
Another solution here
Like @jezrael mentioned before, Pandas do provide API pd.Series.to_frame.
Step 1
You can also wrap the pd.Series to pd.DataFrame by just doing
df_val_counts = pd.DataFrame(value_counts) # wrap pd.Series to pd.DataFrame
Then, you have a pd.DataFrame with column name 'a', and your first column become the index
Input: print(df_value_counts.index.values)
Output: [2 1]
Input: print(df_value_counts.columns)
Output: Index(['a'], dtype='object')
Step 2
What now?
If you want to add new column names here, as a pd.DataFrame, you can simply reset the index by the API of reset_index().
And then, change the column name by a list by API df.coloumns
df_value_counts = df_value_counts.reset_index()
df_value_counts.columns = ['unique_values', 'counts']
Then, you got what you need
Output:
unique_values counts
0 2 3
1 1 2
Full Answer here
import pandas as pd
df = pd.DataFrame({'a':[1, 1, 2, 2, 2]})
value_counts = df['a'].value_counts(dropna=True, sort=True)
# solution here
df_val_counts = pd.DataFrame(value_counts)
df_value_counts_reset = df_val_counts.reset_index()
df_value_counts_reset.columns = ['unique_values', 'counts'] # change column names
I’ll throw in my hat as well, essentially the same as @wy-hsu solution, but in function format:
def value_counts_df(df, col):
"""
Returns pd.value_counts() as a DataFrame
Parameters
----------
df : Pandas Dataframe
Dataframe on which to run value_counts(), must have column `col`.
col : str
Name of column in `df` for which to generate counts
Returns
-------
Pandas Dataframe
Returned dataframe will have a single column named "count" which contains the count_values()
for each unique value of df[col]. The index name of this dataframe is `col`.
Example
-------
>>> value_counts_df(pd.DataFrame({'a':[1, 1, 2, 2, 2]}), 'a')
count
a
2 3
1 2
"""
df = pd.DataFrame(df[col].value_counts())
df.index.name = col
df.columns = ['count']
return df
pd.DataFrame(
df.groupby(['groupby_col'])['column_to_perform_value_count'].value_counts()
).rename(
columns={'old_column_name': 'new_column_name'}
).reset_index()
Example of selecting a subset of columns from a dataframe, grouping, applying value_count per group, name value_count column as Count, and displaying first n groups.
# Select 5 columns (A..E) from a dataframe (data_df).
# Sort on A,B. groupby B. Display first 3 groups.
df = data_df[['A','B','C','D','E']].sort_values(['A','B'])
g = df.groupby(['B'])
for n,(k,gg) in enumerate(list(g)[:3]): # display first 3 groups
display(k,gg.value_counts().to_frame('Count').reset_index())
Hi I want to get the counts of unique values of the dataframe. count_values implements this however I want to use its output somewhere else. How can I convert .count_values output to a pandas dataframe. here is an example code:
import pandas as pd
df = pd.DataFrame({'a':[1, 1, 2, 2, 2]})
value_counts = df['a'].value_counts(dropna=True, sort=True)
print(value_counts)
print(type(value_counts))
output is:
2 3
1 2
Name: a, dtype: int64
<class 'pandas.core.series.Series'>
What I need is a dataframe like this:
unique_values counts
2 3
1 2
Thank you.
Use rename_axis for name of column from index and reset_index:
df = df.value_counts().rename_axis('unique_values').reset_index(name='counts')
print (df)
unique_values counts
0 2 3
1 1 2
Or if need one column DataFrame use Series.to_frame:
df = df.value_counts().rename_axis('unique_values').to_frame('counts')
print (df)
counts
unique_values
2 3
1 2
I just run into the same problem, so I provide my thoughts here.
Warning
When you deal with the data structure of Pandas, you have to aware of the return type.
Another solution here
Like @jezrael mentioned before, Pandas do provide API pd.Series.to_frame.
Step 1
You can also wrap the pd.Series to pd.DataFrame by just doing
df_val_counts = pd.DataFrame(value_counts) # wrap pd.Series to pd.DataFrame
Then, you have a pd.DataFrame with column name 'a', and your first column become the index
Input: print(df_value_counts.index.values)
Output: [2 1]
Input: print(df_value_counts.columns)
Output: Index(['a'], dtype='object')
Step 2
What now?
If you want to add new column names here, as a pd.DataFrame, you can simply reset the index by the API of reset_index().
And then, change the column name by a list by API df.coloumns
df_value_counts = df_value_counts.reset_index()
df_value_counts.columns = ['unique_values', 'counts']
Then, you got what you need
Output:
unique_values counts
0 2 3
1 1 2
Full Answer here
import pandas as pd
df = pd.DataFrame({'a':[1, 1, 2, 2, 2]})
value_counts = df['a'].value_counts(dropna=True, sort=True)
# solution here
df_val_counts = pd.DataFrame(value_counts)
df_value_counts_reset = df_val_counts.reset_index()
df_value_counts_reset.columns = ['unique_values', 'counts'] # change column names
I’ll throw in my hat as well, essentially the same as @wy-hsu solution, but in function format:
def value_counts_df(df, col):
"""
Returns pd.value_counts() as a DataFrame
Parameters
----------
df : Pandas Dataframe
Dataframe on which to run value_counts(), must have column `col`.
col : str
Name of column in `df` for which to generate counts
Returns
-------
Pandas Dataframe
Returned dataframe will have a single column named "count" which contains the count_values()
for each unique value of df[col]. The index name of this dataframe is `col`.
Example
-------
>>> value_counts_df(pd.DataFrame({'a':[1, 1, 2, 2, 2]}), 'a')
count
a
2 3
1 2
"""
df = pd.DataFrame(df[col].value_counts())
df.index.name = col
df.columns = ['count']
return df
pd.DataFrame(
df.groupby(['groupby_col'])['column_to_perform_value_count'].value_counts()
).rename(
columns={'old_column_name': 'new_column_name'}
).reset_index()
Example of selecting a subset of columns from a dataframe, grouping, applying value_count per group, name value_count column as Count, and displaying first n groups.
# Select 5 columns (A..E) from a dataframe (data_df).
# Sort on A,B. groupby B. Display first 3 groups.
df = data_df[['A','B','C','D','E']].sort_values(['A','B'])
g = df.groupby(['B'])
for n,(k,gg) in enumerate(list(g)[:3]): # display first 3 groups
display(k,gg.value_counts().to_frame('Count').reset_index())