A Hands-on Introduction to R

OSCON 2013 Speaker Series

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R is an open-source statistical computing environment similar to SAS and SPSS that allows for the analysis of data using various techniques like sub-setting, manipulation, visualization and modeling. There are versions that run on Windows, Mac OS X, Linux, and other Unix-compatible operating systems.

To follow along with the examples below, download and install R from your local CRAN mirror found at r-project.org. You’ll also want to place the example CSV into your Documents folder (Windows) or home directory (Mac/Linux).

After installation, open the R application. The R Console will pop-up automatically. This is where R code is processed. To begin writing code, open an editor window (File -> New Script on Windows or File -> New Document on a Mac) and type the following code into your editor:

Place your cursor anywhere on the “1+1” code line, then hit Control-R (in Windows) or Command-Return (in Mac). You’ll notice that your “1+1” code is automatically executed in the R Console. This is the easiest way to run code in R. You can also run R code by typing the code directly into your R Console, but using the editor is much easier.

If you want to refresh your R Console, click anywhere inside of it and hit Control-L (in Windows) or Command-Option-L (in Mac).

Now let’s create a Vector, the simplest possible data structure in R. A Vector is similar to a column of data inside a spreadsheet. We use the combine function to do so:

To view the contents of raysVector, just run the line of code above. After running the code shown above, double-click on raysVector (in the editor) and then run the code that is automatically highlighted after double-clicking. You will now see the contents of raysVector in your R Console.

The object we just created is now stored in memory and we can see this by running the following code:

R is an interpreted language with support for procedural and object-oriented programming. Here we use the mean statistical function to calculate the statistical mean of raysVector:

Getting help on the mean function is easy using:

We can create a simple plot of raysVector using:

Importing CSV files is simple too:

We can subset the CSV data in many different ways. Here are two different methods that do the same thing:

There are many ways to transform your data in R. Here’s a method that doubles everyone’s age:

The apply function allows us to apply a standard or custom function without loops. Here we apply the mean function column-wise to the first 3 rows of the dataset in order to analyze the age and height columns of the dataset. We will also ignore missing values during the calculation:

Here we build a linear regression model that predicts a person’s weight based on their age and height:

We can plot our residuals like this:

We can install the Predictive Model Markup Language (PMML) package to quickly deploy our predictive model in a Business Intelligence system without custom SQL:

After running the code above, you may need to select a mirror if this is the first time you are installing an R package on your system. Select any mirror you like.

After installing the pmml package, we now load the package into memory – so we can use the package:

Now we export our regression model to PMML format, which is an open-standard format based on XML. The PMML file will export to your working directory after running the following code:

If you are unsure where your working directory is located, just run this code:

If you want to learn more about PMML, here is a short video that provides a high-level explanation.

As you can see, it’s pretty easy to get going with R. It allows you to get right to manipulating data and converting it to a usable format is a breeze.

http://www.youtube.com/watch?v=kATcvRhoO-Q

NOTE: If you are interested in attending OSCON to check out Ray’s talk or the many other cool sessions, click over to the OSCON website where you can use the discount code OS13PROG to get 20% off your registration fee.

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