[Rd] model.matrix.default chokes on backquote (PR#7202)

ggrothendieck at myway.com ggrothendieck at myway.com
Sat Aug 28 06:05:48 CEST 2004

Full_Name: Gabor Grothendieck
Version: R version 1.9.1, 2004-08-03
OS: Windows XP
Submission from: (NULL) (

The following gives an error:

	> `a(b)` <- 1:4
	> `c(d)` <- (1:4)^2
	> lm(`a(b)` ~ `c(d)`)
	Error in model.matrix.default(mt, mf, contrasts) : 
        	model frame and formula mismatch in model.matrix()

To fix it replace this line in model.matrix.default:

	reorder <- match(attr(t, "variables")[-1], names(data))

with these two lines:

	strip.backquote <- function(x) gsub("^`(.*)`", "\\1", x)
	reorder <- match(strip.backquote(attr(t, "variables"))[-1], 

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