Book Image

R for Data Science Cookbook (n)

By : Yu-Wei, Chiu (David Chiu)
Book Image

R for Data Science Cookbook (n)

By: Yu-Wei, Chiu (David Chiu)

Overview of this book

This cookbook offers a range of data analysis samples in simple and straightforward R code, providing step-by-step resources and time-saving methods to help you solve data problems efficiently. The first section deals with how to create R functions to avoid the unnecessary duplication of code. You will learn how to prepare, process, and perform sophisticated ETL for heterogeneous data sources with R packages. An example of data manipulation is provided, illustrating how to use the “dplyr” and “data.table” packages to efficiently process larger data structures. We also focus on “ggplot2” and show you how to create advanced figures for data exploration. In addition, you will learn how to build an interactive report using the “ggvis” package. Later chapters offer insight into time series analysis on financial data, while there is detailed information on the hot topic of machine learning, including data classification, regression, clustering, association rule mining, and dimension reduction. By the end of this book, you will understand how to resolve issues and will be able to comfortably offer solutions to problems encountered while performing data analysis.
Table of Contents (19 chapters)
R for Data Science Cookbook
About the Author
About the Reviewer

Merging large datasets with a data.table

In previous recipes, we demonstrated how to manipulate and aggregate data with a data.table. In addition to performing data manipulation on a single table, we often need to import additional features or correlate data from other data sources. Therefore, we can join two or more tables into one. In this recipe, we introduce some methods that we can use to merge two data.table.

Getting ready

Ensure that you completed the Enhancing a data.frame with a data.table recipe to load and as both data.frame and data.table into your R environment.

How to do it…

Perform the following steps to merge two data.table:

  1. First, we generate a product.dt data table by calculating the number of purchased items:

    > product.dt <- order.dt[,.(Buy = length(Action)),by=Product]
    > head(product.dt[order(-Buy)])
              Product Buy
    1:    P0005772981 821
    2:    P0024239865 729
    3:    P0004607050 584
    4:    P0003425855 552
    5:    P0014252066 438...