# PDF Project R

What makes R particularly powerful is that statisticians and statistically minded people around the world have contributed more than 8, packages to the R Group and maintain a very active news group offering suggestions and help.

The growing collection of packages and the ease with which they interact with each other and the core R is perhaps the greatest advantage of R. Advanced features include correlational packages for multivariate analyses including Factor and Principal Components Analysis, and cluster analysis. Advanced multivariate analyses packages that have been contributed to the R-project include at least three for Structural Equation Modeling sem , lavaan , and Open-Mx , Multi-level modeling also known as Hierarchical Linear Modeling and referred to as non linear mixed effects in the nlme4 package and taxometric analysis.

Many of the functions described in this tutorial are incorporated into the psych package. Other packages useful for psychometrics are described in a task-view at CRAN. In addition to be a environment of prepackaged routines, R is a interpreted programming language that allows one to create specific functions when needed. In addition to be a package of routines, R is a interpreted programming language that allows one to create specific functions when needed.

This does not require great skills at programming and allows one to develop short functions to do repetitive tasks. R is also an amazing program for producing statistical graphics.

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A collection of some of the best graphics was available at addictedtoR with a complete gallery of thumbnail of figures. This seems to have vanished. However, the site R graph Gallery is worth visiting. An introduction to R is available as a pdf or as a paper back. It is worth reading and rereading. Once R is installed on your machine, the introduction may be obtained by using the help.

More importantly for the novice, a number of very helpful tutorials have been written for R. The Baron and Li tutorial is the most useful for psychologists trying to learn R. Another useful resource is John Fox's short course on R.

### Welcome to R-omania Team

There are a number of "reference cards" also known as "cheat sheets" that provide quick summaries of commands. Jonathan Baron's one pager Tom Short's four pager Paul Torfs and Claudia Brauer not so short introduction More locally, I have taken tutorials originally written by Roger Ratcliff and various graduate students on how to do analysis of variance using S and adapated them to the R environment. This guide was developed to help others learn R, and also to help students in Research Methods , Personality Research , Psychometric Theory , Structural Equation Modeling , or other courses do some basic statisics.

To download a copy of the software, go to the download section of the cran. A detailed pdf of how to download R and some of the more useful packages is available as part of the personality-project. See his post here. He also has written various tutorials on using R for regression and analysis of variance.

Their pages were very useful when I started to learn R. There is a growing number of text books that introduce R. Ripley and William N. For the psychometrically minded, my psychometrics text in progress has all of its examples in R. The R help listserve is a very useful source of information. Just lurking will lead to the answers for many questions. Much of what is included in this tutorial was gleaned from comments sent to the help list. The most frequently asked questions have been organized into a FAQ.

The archives of the help group are very useful and should be searched before asking for help. Jonathan Baron maintains a searchable database of the help list serve. Back to Top R is not overly user friendly at first. Its error messages are at best cryptic. It is, however, very powerful and once partially mastered, easy to use. And it is free. More importantly as additional modules are added, it becomes even more useful. Modules included allow for multilevel hierarchical linear modeling, confirmatory factor analysis, etc. I believe that it is worth the time to learn how to use it.

Baron and Y. Li's guide is very helpful.

They include a one page pdf summary sheet of commands that is well worth printing out and using. A three page summary sheet of commands is available from Rpad. These steps are not meant to limit what can be done with R, but merely to describe how to do the analysis for the most basic of research projects and to give a first experience with R. Although it is possible that your local computer lab already has R, it is most useful to do analyses on your own machine.

In this case you will need to download the R program from the R project and install it yourself. This will take you to list of mirror sites around the world. You may download the Windows, Linux, or Mac versions at this site. For most users, downloading the binary image is easiest and does not require compiling the program. Once downloaded, go through the install options for the program. One of the great strengths of R is that it can be supplemented with additional programs that are included as packages using the package manager.

Most packages are directly available through the CRAN repository. Others are available at the BioConductor repository. The psych package Revelle, - may be downloaded from CRAN or from the personality project repository. For instance, the install. To install the Psychometrics task view.

## The R Project for Statistical Computing - Romania Team

For any other than the default packages to work, you must activate it by either using the Package Manager or the library command, e. If you routinely find yourself using the same packages everytime you use R, you can modify the Startup process by specifying what should happen. Thus, if you always want to have psych available,.

First and then when you quit, use the save workspace option. Help and Guidance R is case sensitive and does not give overly useful diagnostic messages. When in doubt, use the help function. This is identical to the? All packages and all functions will have an associated help window. Each help window will give a brief description of the function, how to call it, the definition of all of the available parameters, a list and definition of the possible output, and usually some useful examples.

One can learn a great deal by using the help windows, but if they are available, it is better to study the package vignette. Package vignettes All packages have help pages for each function in the package. These are meant to help you use a function that you already know about, but not to introduce you to new functions. An increasing number of packages have a package vignettes that give more of an overview of the program than a detailed description of any one function.

These vignettes are accessible from the help window and sometimes as part of the help index for the program. The two vignettes for the psych package are also available from the personality project web page. An overview of the psych package and Using the psych package as a front end to the sem package. Commands are entered into the "R Console" window. You can add a comment to any line by using a. The Mac version has a text editor window that allows you to write, edit and save your commands.

## Project.R - Wikipedia

Alternatively, if you use a normal text editor As a Mac user, I use BBEDIT, PC users can use Notepad , you can write out the commands you want to run, comment them so that you can remember what they do the next time you run a similar analysis, and then copy and paste into the R console. Although being syntax driven seems a throwback to an old, pre Graphical User Interface type command structure, it is very powerful for doing production statistics. Once you get a particular set of commands to work on one data file, you can change the name of the data file and run the entire sequence again on the new data set.

This is is also very helpful when doing professional graphics for papers. In addition, for teaching, it is possible to prepare a web page of instructional commands that students can then cut and paste into R to see for themselves how things work. That is what may be done with the instructions on this page. It is also possible to write text in latex with embedded R commands. Then executing the Sweave function on that text file will add the R output to the latex file.

This almost magical feature allows rapid integration of content with statistical techniques.

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More importantly, it allows for "reproducible research" in that the actual data files and instructions may be specified for all to see. As you become more adept in using R, you will be tempted to enter commands directly into the console window. I think it is better to keep annotated copies of your commands to help you next time. Not necessary, but useful. Help and Guidance For a list of all the commands that use a particular word, use the apropos command: apropos table lists all the commands that have the word "table" in them apropos table [1]"ftable" "model.

A very nice example is demo graphics which shows many of the complex graphics that are possible to do. Back to Top There are multiple ways of reading data into R.