Re: [Rd] problem using model.frame()

From: Gabor Grothendieck <ggrothendieck_at_gmail.com>
Date: Tue 16 Aug 2005 - 15:25:01 GMT

It can handle data frames like this:

        model.frame(y1)
or

        model.frame(~., y1)

On 8/16/05, Gavin Simpson <gavin.simpson@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.
> %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%
>
> ______________________________________________
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>



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https://stat.ethz.ch/mailman/listinfo/r-devel Received on Wed Aug 17 01:28:37 2005

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