#### 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.
R for Data Science Cookbook
Credits
www.PacktPub.com
Preface
Free Chapter
Functions in R
Data Preprocessing and Preparation
Visualizing Data with ggplot2
Making Interactive Reports
Simulation from Probability Distributions
Statistical Inference in R
Time Series Mining with R
Index

## Cutting tree into clusters

In a dendrogram, we can see the hierarchy of clusters, but we have not grouped data into different clusters yet. However, we can determine how many clusters are within the dendrogram and cut the dendrogram at a certain tree height to separate data into different groups. In this recipe, we demonstrate how to use the `cutree` function to separate data into a given number of clusters.

In order to perform the `cutree` function, one needs to have completed the previous recipe by generating an hclust object, `hc`.

### How to do it…

Please perform the following steps to cut the hierarchy of clusters into a given number of clusters:

1. First, categorize the data into three groups:

```> fit <- cutree(hc, k = 3)
```
2. You can then examine the cluster labels for the data:

```> fit
```
3. Count the number of data points within each cluster:

```> table(fit)
fit
1  2  3
18 66 18
```
4. Make a scatter plot with fitted cluster information:

```> plot(hotel\$lon, hotel\$lat, col=fit)
```

Figure 5: The...