Book Image

Learning Predictive Analytics with R

By : Eric Mayor
Book Image

Learning Predictive Analytics with R

By: Eric Mayor

Overview of this book

This book is packed with easy-to-follow guidelines that explain the workings of the many key data mining tools of R, which are used to discover knowledge from your data. You will learn how to perform key predictive analytics tasks using R, such as train and test predictive models for classification and regression tasks, score new data sets and so on. All chapters will guide you in acquiring the skills in a practical way. Most chapters also include a theoretical introduction that will sharpen your understanding of the subject matter and invite you to go further. The book familiarizes you with the most common data mining tools of R, such as k-means, hierarchical regression, linear regression, association rules, principal component analysis, multilevel modeling, k-NN, Naïve Bayes, decision trees, and text mining. It also provides a description of visualization techniques using the basic visualization tools of R as well as lattice for visualizing patterns in data organized in groups. This book is invaluable for anyone fascinated by the data mining opportunities offered by GNU R and its packages.
Table of Contents (23 chapters)
Learning Predictive Analytics with R
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Exercises and Solutions
Index

Multilevel modeling in R


Now that we have examined (laconically) the basics of multilevel modeling equations, we can turn to how to build multilevel models in R and predict unseen data.

For this purpose, we will first load our dataset produced using the same procedure as mentioned previously (except that the attributes are not scaled). Here again, there are 100 generated observations for each of the 17 hospitals:

NursesML = read.table("NursesML.dat", header = T, sep = " ")

The null model

We will examine the variation in our attributes considering hospitals and observations as a unit of analysis, that is, we will compare whether there is more variation at the hospital and observation levels. What we could do is compute this by hand.

The following will compute the mean for the attribute we want to predict (WorkSat) for each of the hospitals:

means = aggregate(NursesML[,4], by=list(NursesML[,5]), 
   FUN=mean)[2]

We can display the variance of work satisfaction in hospitals and observations as follows...