The correct answer is A. Convert wide data to long format.
The melt function in Pandas is used to convert wide data to long format. Wide data is a data structure where each row represents an observation and each column represents a variable. Long data is a data structure where each row represents a variable and each column represents an observation.
The melt function takes two arguments: a DataFrame and a column name. The DataFrame is the data that you want to convert to long format. The column name is the name of the column that you want to use as the index of the long data.
The melt function returns a new DataFrame in long format. The new DataFrame will have one row for each variable and one column for each observation. The values in the new DataFrame will be the values from the original DataFrame, but they will be organized in a different way.
Here is an example of how to use the melt function:
“`
import pandas as pd
df = pd.DataFrame({‘A’: [1, 2, 3], ‘B’: [4, 5, 6], ‘C’: [7, 8, 9]})
melted_df = pd.melt(df, id_vars=[‘A’], var_name=’B’, value_name=’C’)
print(melted_df)
A B C
0 1 4 7
1 2 5 8
2 3 6 9
“`
The melted_df DataFrame has one row for each variable (A, B, and C) and one column for each observation (1, 2, and 3). The values in the melted_df DataFrame are the values from the original DataFrame, but they are organized in a different way.