[R] pls help to print out first row of terms(model) output in example program

[William Dunlap]

Does applying formula() to the output of lm() (or terms())
do what you want?
  > d <- data.frame(y=1:10, x1=log(1:10), x2=sqrt(1:10), x3=1/(1:10))
  > formula(lm(formula("y~."), data=d)) # dot expanded
  y ~ x1 + x2 + x3
  > lm(formula("y~."), data=d)$call[[2]] # your original
  formula("y~.")
  > lm(formula("y~."), data=d)$call$formula # a better version of original
  formula("y~.")

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com 

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of Paul Johnson
> Sent: Monday, December 19, 2011 1:15 PM
> To: R-help
> Subject: [R] pls help to print out first row of terms(model) output in example program
> 
> Greetings.
> 
> I've written a convenience function for multicollinearity diagnosis.
> I'd like to report to the user the formula that is used in a
> regression.  I get output like this:
> 
> > mcDiagnose(m1)
> [1] "The following auxiliary models are being estimated and returned in a list:"
> [1] "`x1` ~ ."
> formula(fmla)()
> [1] "`x2` ~ ."
> 
> I'd like to fill in the period with the variable names that are in there.
> 
> I know the information is in there, I just need to get it.  The terms
> output for a fitted model has the output at the very top, in the first
> line, above the attributes.  I just want to print out that first line,
> here:
> 
> > terms(m2)
> y ~ log(10 + x1) + poly(x2, 2)
> attr(,"variables")
> list(y, log(10 + x1), poly(x2, 2))
> attr(,"factors")
>              log(10 + x1) poly(x2, 2)
> y                       0           0
> log(10 + x1)            1           0
> poly(x2, 2)             0           1
> attr(,"term.labels")
> [1] "log(10 + x1)" "poly(x2, 2)"
> [snip]
> 
> In my working example code below , I need the help where I have "##fix
> me fix me##
> 
> 
> ##Paul Johnson
> ## 2011-12-19
> ## mcDiagnose.R
> 
> lmAuxiliary <- function(model){
>   dat <- as.data.frame(model.matrix(model))
>   ## ivnames <- attr(delete.response(terms(model)), "term.labels")
>   ## previous does not work with transforms like poly
>   hasIntercept <- attr(terms(model), "intercept")
> 
>   if (hasIntercept) dat <- dat[ , -1] # removes intercept. assumes
> intercept in column 1
>   ivnames <- colnames(dat)
>   print("The following auxiliary models are being estimated and
> returned in a list:")
> 
>   results <- list()
> 
>   for (i in ivnames) {
>     fmla <- paste( "`", i, "`", " ~ ." , sep="");
>     print(fmla)
>     maux <- lm( formula(fmla), data=dat)
>     results[[ i ]] <- maux
>     print(maux$call[2])
>     ###fix me fix me ##
>   }
>   results
> }
> 
> 
> mcDiagnose <- function(model){
>   auxRegs <- lmAuxiliary(model)
>   auxRsq <- numeric(length=length(auxRegs))
>   j <- 0
>   for ( i in auxRegs ){
>     j <- j + 1
>     sumry <- summary(i)
>     auxRsq[j] <- sumry$r.squared
>   }
>   print("Drum roll please!")
>   print("And your R_j Squareds are (auxiliary Rsq)")
>   print(names(auxRegs))
>   print(auxRsq)
> }
> 
> x1 <- rnorm(100)
> x2 <- rnorm(100)
> y <- rnorm(100)
> 
> m1 <- lm(y~x1+x2)
> 
> mcDiagnose(m1)
> 
> 
> m2 <- lm(y~log(10+x1) + poly(x2,2))
> 
> mcDiagnose(m2)
> 
> --
> Paul E. Johnson
> Professor, Political Science
> 1541 Lilac Lane, Room 504
> University of Kansas
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.