[R] Error in model.frame

[Martyn Plummer]

On Wed, 2003-12-10 at 10:34, Göran Broström wrote:
> I recently ran into the following:
> 
> > x <- c(1,2,4,3)
> > lm(x ~ 1:length(x))
> Error in model.frame(formula, rownames, variables, varnames, extras, extranames,  : 
>         variable lengths differ
> 
> but
> 
> > lm(x ~ c(1:length(x)))
> 
> Call:
> lm(formula = x ~ c(1:length(x)))
> 
> Coefficients:
>    (Intercept)  c(1:length(x))  
>            0.5             0.8  
> 
> and
> 
> > identical(1:4, c(1:4))
> [1] TRUE
> 
> Should I report this as a bug?

No. In a formula ":" is interpreted differently.
It is used to represent interactions. See help(formula).
It is probably good practice to generate variables outside of
the formula and then refer to them by name.

Martyn