Is it possible to make print.formula respect the environment width option?

The formula print method does not respect the environment width option.

For example, given the following long formula:

fo <- y ~ factor1 + factor2 + factor3 + factor4 + factor5 + factor6 + factor7 + factor8

Set the environment width fairly narrow

options(width=30)

And print the formula

print(fo)

Results开发者_开发技巧 in (regardless of the width option)

y ~ factor1 + factor2 + factor3 + factor4 + factor5 + factor6 + 
    factor7 + factor8

Any ideas how to make print.formula respect the width option?

You can use a combination of strwrap and capture.output:

fo <- y ~ factor1 + factor2 + factor3 + factor4 + factor5 + factor6 + factor7 + factor8
options(width=30)
strwrap(capture.output(print(fo)))

[1] "y ~ factor1 + factor2 +"
[2] "factor3 + factor4 +"    
[3] "factor5 + factor6 +"    
[4] "factor7 + factor8"      

You could hack around with print.formula, but the easiet thing to do is to wrap the output in strwrap, which does respect getOption("width").

cat(strwrap(fo), sep = "\n")

Conversion to character transposes the first two elements, so you need to do a little fixing up first.

ch_fo <- paste(as.character(fo)[c(2,1,3)], collapse = " ")
cat(strwrap(ch_fo), sep = "\n")

Using deparse is another option.

deparse(fo, width.cutoff = getOption('width'))

I ended up going with a sightly different approach:

print.f <- function(f) { 
  cat(paste(deparse(f, width.cutoff=getOption("width")), collapse="\n")) 
}

It respects the environment's width setting, while printing the naked (not a string vector) formula with correct indenting.