[R] Error in gam?

[Hadley Wickham]

I'm having some problems using variable names containing spaces (using 
backticks) with gam (mgcv 0.9-6, R 1.8.1).  Some toy code to reproduce 
my problem is below.  Am I doing something wrong, or should I pass this 
bug on to Simon Wood? (Or do I need to rename my variables to get rid of 
the spaces?)

Thanks,

Hadley


library(mgcv)

test <- data.frame(a = c(1:10), `a b` = c(1:10)^2, c=2:11, check.names=F)
test$`a b`

lm(a ~ `a b`, data=test) #works
gam(a ~ s(c), data=test) #works
gam(a ~ s(`a b`), data=test) #error below

Error in parse(file, n, text, prompt) : parse error

traceback()
  9: parse(text = x)
  8: eval(parse(text = x)[[1]])
  7: formula(eval(parse(text = x)[[1]]))
  6: switch(mode(x), "NULL" = structure(NULL, class = "formula"),
        character = formula(eval(parse(text = x)[[1]])), call = eval(x),
        stop("invalid formula"))
5: formula.default(object, env = NULL)
4: formula(object, env = NULL)
3: as.formula(rf)
2: gam.parser(formula)
1: gam(a ~ s(`a b`), data = test)