R help - Dec 2011 - 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

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
> 
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