# tutorial

### R Tutorial Series: Regression With Interaction Variables

January 23, 2010 |

Interaction variables introduce an additional level of regression analysis by allowing researchers to explore the synergistic effects of combined predictors. This tutorial will explore how interaction models can be created in R.Tutorial Files Before we... [Read more...]

### R Tutorial Series: Hierarchical Linear Regression

January 15, 2010 |

Regression models can become increasingly complex as more variables are included in an analysis. Furthermore, they can become exceedingly convoluted when things such as polynomials and interactions are explored. Thankfully, once the potential independe... [Read more...]

### Pivot tables in R

January 9, 2010 |

A common data-munging operation is to compute cross tabulations of measurements by categories. SQL Server and Excel have a nice feature called pivot tables for this purpose. Here we'll figure out how to do pivot operations in R.Let's imagine an experim...

### R Tutorial Series: ANOVA Tables

January 8, 2010 |

The commonly applied analysis of variance procedure, or ANOVA, is a breeze to conduct in R. This tutorial will explore how R can be used to perform ANOVA to analyze a single regression model and to compare multiple models.Tutorial FilesBefore we begin,...

### R: Memory usage statistics by variable

January 4, 2010 |

Do you need a way to find out which individual variables in R consume the most memory? # create dummy variables for demonstration x [Read more...]

### SQL group by in R

December 27, 2009 |

The R statistical computing environment is awesome, but weird. How to do database operations in R is a common source of questions. The other day I was looking for an equivalent to SQL group by for R data frames. You need this to compute summary statist...

### Compare performance of machine learning classifiers in R

December 23, 2009 |

This tutorial demonstrates to the R novice how to create five machine learning models for classification and compare the performance graphically with ROC curves in one chart. For a simpler introduction, start with Plot ROC curve and lift chart in R. # ... [Read more...]

### Plot ROC curve and lift chart in R

December 18, 2009 |

This tutorial with real R code demonstrates how to create a predictive model using cforest (Breiman’s random forests) from the package party, evaluate the predictive model on a separate set of data, and then plot the performance using ROC curves ... [Read more...]

### Joining data frames in R

December 17, 2009 |

Want to join two R data frames on a common key? Here's one way do a SQL database style join operation in R.We start with a data frame describing probes on a microarray. The key is the probe_id and the rest of the information describes the location on ...

### R Tutorial Series: Graphic Analysis of Regression Assumptions

December 15, 2009 |

An important aspect of regression involves assessing the tenability of the assumptions upon which its analyses are based. This tutorial will explore how R can help one scrutinize the regression assumptions of a model via its residuals plot, normality h... [Read more...]

### R Tutorial Series: Multiple Linear Regression

December 8, 2009 |

In R, multiple linear regression is only a small step away from simple linear regression. In fact, the same lm() function can be used for this technique, but with the addition of a one or more predictors. This tutorial will explore how R can be used to...

### R Tutorial Series: Simple Linear Regression

November 26, 2009 |

Simple linear regression uses a solitary independent variable to predict the outcome of a dependent variable. By understanding this, the most basic form of regression, numerous complex modeling techniques can be learned. This tutorial will explore how ...

### R examine objects tutorial

November 21, 2009 |

This article is quick concrete example of how to use the techniques from Survive R to lower the steepness of The R Project for Statistical Computing‘s learning curve (so an apology to all readers who are not interested in R). What follows is for people who already use R ... [Read more...]

### R Tutorial Series: Scatterplots

November 12, 2009 |

A scatterplot is a useful way to visualize the relationship between two variables. Similar to correlations, scatterplots are often used to make initial diagnoses before any statistical analyses are conducted. This tutorial will explore the ways in whic...

### R Tutorial Series: Zero-Order Correlations

November 6, 2009 |

One of the most common and basic techniques for analyzing the relationships between variables is zero-order correlation. This tutorial will explore the ways in which R can be used to employ this method.Tutorial FilesBefore we start, you may want to dow...

### R Tutorial Series: Introduction to The R Project for Statistical Computing (Part 2)

October 15, 2009 |

Welcome to part two of the Introduction to The R Project for Statistical Computing tutorial. If you missed part one, it can be found here. In this segment, we will explore the following topics.Importing DataVariablesWorkspace FilesConsole FilesFinding ... [Read more...]

### R Tutorial Series: Introduction to The R Project for Statistical Computing (Part 1)

October 11, 2009 |

R is a free, cross-platform, open-source statistical analysis language and program. It is also an alternative to expensive commercial statistics software such as SPSS. The environment for R differs from the typical point and click interface found in mo... [Read more...]

### Delete rows from R data frame

October 8, 2009 |

Deleting rows from a data frame in R is easy by combining simple operations. Let’s say you are working with the built-in data set airquality and need to remove rows where the ozona is NA (also called null, blank or missing). The method is a conce... [Read more...]

### R String processing

July 2, 2009 |

Here's a little vignette of data munging using the regular expression facilities of R (aka the R-project for statistical computing). Let's say I have a vector of strings that looks like this:__ coords [1] "chromosome+:157470-158370" "chromosome+:1583...