Information about downloading, installing, running, learning, and using xxM.

Install Software

R

xxM is currently available as an R-package complied for 32 bit R version 3.x.x.  It has been tested with R 3.0.2 and R 3.1.1.  It should work with version 3 of R.  The xxM package may not install if both 32 bit and 64 bit versions of R are installed on your machine.  However, if you are using Rstudio, you can install multiple versions of R and select 32 bit R for xxM.  R can be downloaded from the R-project website.

Rstudio

Rstudio is an excellent IDE for R.  It is practically indispensable.  Instructions for setting-up R and Rstudio for xxM. Once R and Rstudio are both installed, you set 32 bit version of R as the default from within RStudio:

1. Click menu “Tools” >> “Global Options…”
2. Under “R General” tab, the first field is “R version”.
   • If the R version is “[32-bit] C:\Program Files\R\R-3.x.x”, you are all set.
   • If it shows [64-bit], click “Change…” and select “Use your machine’s default version of R (32-bit)”.
   • In case, the default version is not set in the registry, Select any [32-bit] R version from the list “Choose a specific version of R” .
   • You will need to restart Rstudio to change to the new default 32-bit R.

xxM

• Download xxM.
• Install the downloaded “xxm.zip” file from within Rstudio or from the command line:
  install.packages("C://path-to-download//xxm.zip", repos=NULL)

Join Our Community

• If you have not already done so, please join our community. Members will be able to post comments and participate in the user’s group. You will also receive notifications about updates.
• Create an account.
• Login as a member.
• In case of issues with the website, please send an email to [paras-dot-mehta-at-times-dot-uh-dot-edu].

Learn xxM

Work through quick-start tutorial

Perhaps the best way to get started with xxM is to work-through the “bivariate random-intercepts model” in the example section.  Once you are able to reproduce the results of the example by running the xxM script with the packaged dataset, you will be ready to start using xxM on your own.

Read documentation

• The package comes with many fully documented examples of various Multilevel structural equation models (ML-SEM).  The datasets and working scripts for each example is included under models directory of the installed package.
• “xxM User’s Guide” is included under documentation folder and includes a detailed description of each model, and the corresponding xxM script.
• The package also includes a built-in R package reference which can be displayed by typing ??xxm at the command prompt. The package documentation includes descriptions of the included datasets and worked example.

Learn by example

Online examples of different multilevel structural equations models aim to complement rather than duplicate information provided in the user’s guide. Each example includes, 

• Description of the model in multiple traditional frameworks (MLM, SEM, LME).
• xxM formulation is described in equations, matrices and path diagram
• xxM script is fully annotated describing each including an annotated log of the complete model fitting session. Each step needed to construct the model is described and the results of the interactive session are provided.

Learn how others have used xxM

• See publications using xxM

Get help

Seek answers

• If you have a question or get an error message check Frequently Asked Questions (FAQ)

Ask questions

• If your question remains unanswered, please post your questions on xxM User’s Forum.
• If you need additional help, feel free to send an email to paras-dot-mehta-at-times-dot-uh-dot -edu.

Talk to us

Give feedback

• Your comments and feedback will be greatly appreciated.

Make suggestions

• Tell us features that you would like to see.

Contribute

• Share your work with the community.
• Share your datasets and script examples with other users.