278 search results for "ANOVA"

Interaction plot from cell means

February 24, 2010
By
Interaction plot from cell means

I needed to produce a few a interaction plots for my book in R and, while the interaction.plot() function is useful it has a couple of drawbacks. First, the default output isn't very pretty. Second, it works from the raw data, whereas I often need plot...

Read more »

Post hoc analysis for Friedman’s Test (R code)

February 22, 2010
By
Post hoc analysis for Friedman’s Test  (R code)

My goal in this post is to give an overview of Friedman’s Test and then offer R code to perform post hoc analysis on Friedman’s Test results. (The R function can be downloaded from here) Preface: What is Friedman’s Test Friedman test is a non-parametric randomized block analysis of variance. Which is to say it is a non-parametric version of...

Read more »

Design of Experiments – Block Designs

February 20, 2010
By
Design of Experiments – Block Designs

In many experiments where the investigator is comparing a set of treatments there is the possibility of one or more sources of variability in the experimental measurements that can be accounted for during the design stage of the experimentation. For example we might be investigating four different pieces of machinery using say two different operators,

Read more »

Gas price seasonality

February 18, 2010
By
Gas price seasonality

Last spring I read “Quantitative Trading” by Ernest P. Chan. In his book, he suggested to buy gas futures contract at the end of February and sell it later, in March. Today, I decided to test this strategy by using R-language. The most important thing for such investigation is data. For this purpose, I used this

Read more »

Making publication-ready tables with xtable

February 12, 2010
By
Making publication-ready tables with xtable

When you use R at the command-line, the textual output is limited by the medium: one monospaced font, with no typesetting of any kind. That's great when you're doing exploratory analysis, but what about when you want to include R output in a report or publication? In other words, what if you want to convert this Analysis of Variance...

Read more »

R Tutorial Series: Basic Polynomial Regression

February 8, 2010
By
R Tutorial Series: Basic Polynomial Regression

Often times, a scatterplot reveals a pattern that seems not so linear. Polynomial regression can be used to explore a predictor at different levels of curvilinearity. This tutorial will demonstrate how polynomial regression can be used in a hierarchical fashion to best represent a dataset in R.Tutorial FilesBefore we begin, you may want to download the sample...

Read more »

R Tutorial Series: Basic Polynomial Regression

February 8, 2010
By
R Tutorial Series: Basic Polynomial Regression

Often times, a scatterplot reveals a pattern that seems not so linear. Polynomial regression can be used to explore a predictor at different levels of curvilinearity. This tutorial will demonstrate how polynomial regression can be used in a hierarchical fashion to best represent a dataset in R.Tutorial FilesBefore we begin, you may want to download the sample...

Read more »

R Tutorial Series: Hierarchical Linear Regression

January 15, 2010
By
R Tutorial Series: Hierarchical Linear Regression

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 »

Latin squares design in R

January 6, 2010
By
Latin squares design in R

The Latin square design is used where the researcher desires to control the variation in an experiment that is related to rows and columns in the field.Remember that: * Treatments are assigned at random within rows and columns, with each treatment once per row and once per column. * There are equal numbers...

Read more »

Latin squares design in R

January 6, 2010
By
Latin squares design in R

The Latin square design is used where the researcher desires to control the variation in an experiment that is related to rows and columns in the field.Remember that: * Treatments are assigned at random within rows and columns, with each treatment once per row and once per column. * There are equal numbers...

Read more »