two new packages

John Fox jfox at
Sat Apr 28 04:51:37 CEST 2001

I've prepared preliminary versions of two packages that I plan eventually 
to contribute to CRAN:

car (for "Companion to Applied Regression") is a package that provides a 
variety of functions in support of linear and generalized linear models, 
including regression diagnostics (e.g., studentized residuals, hat-values, 
Cook's distances, dfbeta, dfbetas, added-variable plots, component+residual 
plots, ceres plots, Durbin-Watson statistics); some tools for graphing and 
exploring data (e.g., enhanced quantile-comparison plots -- with simulated 
envelopes for studentized residuals from linear models, scatterplot, and 
scatterplot-matrix functions); some utilities (e.g., for recoding 
variables); some functions for transformations of data (e.g., multivariate 
unconditional Box-Cox transformation); an enhanced Anova function; and many 
datasets. The object is to make tasks that are commonly employed in 
regression modeling more convenient, particularly for students with limited 
programming skills. I've tried largely to avoid duplicating capabilities in 
existing packages.

sem is a package for fitting "structural-equation models." The package 
supports general structural equation models with latent varibles, fit by 
maximum likelihood assuming multinormality, and single-equation estimation 
for observed-variable models by two-stage least squares.

For the present, I'm making these packages available on my web site, at 
<> and 

I'm particularly interested in suggestions and comments.


  John Fox
  Department of Sociology
  McMaster University
  email: jfox at

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