Lecture Note
University
University of California San DiegoCourse
DSC 207R | Python for Data SciencePages
2
Academic year
2023
anon
Views
5
Live Code, Frequent Data Operations Transform Your Data Analysis with Pandas Pandas is an effective tool for data analysis that offers quick and adaptable data structures. It is the go-to library for the majority of data scientists and analysts and is widelyused for manipulating and analyzing data in Python. We shall examine some of the mostbeneficial transformations that Pandas can carry out in this article. Slicing DataFrames In data analysis, slicing is an essential operation. A subset of rows or columns from a DataFrame can be chosen using this method. Pandas has strong indexing and selectingfeatures that let you manipulate your data in a variety of ways. Let's take an example where you have a DataFrame called tags with a column called tag. The tag column's first few rows should be shown. The head function can be used for thefollowing: tags.head() If you want to select specific columns, you can use the loc accessor: movies.loc[:, [ 'title' , 'genres' ]].head() Here, we are selecting the title and genres columns from the movies DataFrame anddisplaying the first few rows. You can also slice out a portion of a DataFrame by specifying the rows you want: ratings[ 1000 : 1010 ] This will return rows 1000 through 1009 of the ratings DataFrame. You can also use negativeindexing to slice from the end of the DataFrame: ratings[- 10 :] This will return the bottom 10 rows of the ratings DataFrame. Working with Columns Pandas provides many powerful functions for working with columns. For example, if you want to count the occurrences of each unique value in a column, you can use thevalue_counts function:
tag_counts = tags[ 'tag' ].value_counts() tag_counts[: 10 ] This will return the top 10 tags, along with the number of occurrences for each tag. You can also plot the results using Pandas' built-in plot functions: tag_counts[: 10 ].plot(kind= 'bar' ) This will plot a bar chart of the top 10 tags. Filtering DataFrames Filtering is another common operation in data analysis. It is used to select rows based on a certain condition. For example, let's say you want to filter out the movies that have arating of less than 4.0. You can do this using a boolean mask: is_highly_rated = movies[ 'rating' ] >= 4.0 movies[is_highly_rated].head() This will return all the movies that have a rating of 4.0 or higher. Aggregating Data Data are combined into groups through the process of "aggregation," and each group's data are then summarized. Pandas offers robust aggregating features that make it simple foryou to carry out this task. Let's imagine, for illustration purposes, that you wish to locate theaverage rating for each film in the ratings DataFrame. You may group the data by movieIdusing the groupby function, and then use the mean function to calculate the average rating: rating_means = ratings.groupby( 'movieId' )[ 'rating' ].mean() rating_means[: 10 ] This will return the average rating for the top 10 movies in the ratings DataFrame. Conclusion Pandas is an effective tool for data analysis that offers quick and adaptable data structures. We have discussed some of the most practical Pandas transformations in thispost, including data slicing, working with columns, filtering, and aggregation. You can usePandas to rapidly and efficiently analyze and manipulate your data if you become proficientin these procedures. In order to transform, start reading the Pandas manual.
Frequent Data Operations
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