[Rd] problem using model.frame()

[Gabor Grothendieck]

It can handle data frames like this:

	model.frame(y1)
or
	model.frame(~., y1)


On 8/16/05, Gavin Simpson <gavin.simpson at ucl.ac.uk> wrote:
> Hi I'm having a problem with model.frame, encapsulated in this example:
> 
> y1 <- matrix(c(3,1,0,1,0,1,1,0,0,0,1,0,0,0,1,1,0,1,1,1),
>             nrow = 5, byrow = TRUE)
> y1 <- as.data.frame(y1)
> rownames(y1) <- paste("site", 1:5, sep = "")
> colnames(y1) <- paste("spp", 1:4, sep = "")
> y1
> 
> model.frame(~ y1)
> Error in model.frame(formula, rownames, variables, varnames, extras, extranames,  :
>        invalid variable type
> 
> temp <- as.matrix(y1)
> model.frame(~ temp)
>  temp.spp1 temp.spp2 temp.spp3 temp.spp4
> 1         3         1         0         1
> 2         0         1         1         0
> 3         0         0         1         0
> 4         0         0         1         1
> 5         0         1         1         1
> 
> Ideally the above wouldn't have names like temp.var1, temp.var2, but one
> could deal with that later.
> 
> I have tracked down the source of the error message to line 1330 in
> model.c - here I'm stumped as I don't know any C, but it looks as if the
> code is looping over the variables in the formula and checking of they
> are the right "type". So a matrix of variables gets through, but a
> data.frame doesn't.
> 
> It would be good if model.frame could cope with data.frames in formulae,
> but seeing as I am incapable of providing a patch, is there a way around
> this problem?
> 
> Below is the head of the function I am currently using, including the
> function for parsing the formula - borrowed and hacked from
> ordiParseFormula() in package vegan.
> 
> I can work out the class of the rhs of the forumla. Is there a way to
> create a suitable environment for the data argument of parseFormula()
> such that it contains the rhs dataframe coerced to a matrix, which then
> should get through model.frame.default without error? How would I go
> about manipulating/creating such an environment? Any other ideas?
> 
> Thanks in advance
> 
> Gav
> 
> coca.formula <- function(formula, method = c("predictive", "symmetric"),
>                         reg.method = c("simpls", "eigen"), weights = NULL,
>                         n.axes = NULL, symmetric = FALSE, data)
>  {
>    parseFormula <- function (formula, data)
>      {
>        browser()
>        Terms <- terms(formula, "Condition", data = data)
>        flapart <- fla <- formula <- formula(Terms, width.cutoff = 500)
>        specdata <- formula[[2]]
>        X <- eval(specdata, data, parent.frame())
>        X <- as.matrix(X)
>        formula[[2]] <- NULL
>        if (formula[[2]] == "1" || formula[[2]] == "0")
>          Y <- NULL
>        else {
>          mf <- model.frame(formula, data, na.action = na.fail)
>          Y <- model.matrix(formula, mf)
>          if (any(colnames(Y) == "(Intercept)")) {
>            xint <- which(colnames(Y) == "(Intercept)")
>            Y <- Y[, -xint, drop = FALSE]
>          }
>        }
>        list(X = X, Y = Y)
>      }
>    if (missing(data))
>      data <- parent.frame()
>    #browser()
>    dat <- parseFormula(formula, data)
> 
> --
> %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%
> Gavin Simpson                     [T] +44 (0)20 7679 5522
> ENSIS Research Fellow             [F] +44 (0)20 7679 7565
> ENSIS Ltd. & ECRC                 [E] gavin.simpsonATNOSPAMucl.ac.uk
> UCL Department of Geography       [W] http://www.ucl.ac.uk/~ucfagls/cv/
> 26 Bedford Way                    [W] http://www.ucl.ac.uk/~ucfagls/
> London.  WC1H 0AP.
> %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%
> 
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>