similar to: under certain conditions, model.matrix appears to lack one (PR#647)

On Mon, 28 Aug 2000, Rashid Nassar wrote: > Dear Professor Ripley, > > Thank you very much for your kind explanation. If I may lamely say > something in my defence, even as I apologize for my error: I mistook the > sentence "the (quoted) name of a function" to mean "optionally quoted" > because of the parentheses surrounding "quoted", and was

Dear R Team, # Summary of the problem: setting contrasts as > contrasts(g) <- contr.treatment or > contrasts(g) <- matrix(c(1,-1,0),ncol=1) (i.e. without quotes around `contr.treatment' or `contr.sum', etc.) and fitting an lm model without an intercept results in a model matrix that lacks one column. (I do ask for forgiveness if this is not a bug but is due to my

I believe you are right, but can you please explain why anyone would want to fit this model? It differs only in the coding from aov(y ~ a + b + Error(c), data=test.df) and merely lumps together the top two strata. There is a much simpler fix: in the line if(intercept) nmstrata <- c("(Intercept)", nmstrata) remove the condition (and drop the empty stratum later if you

platform: Linux Mandrake 10.0 AMD processor, X11 graphics with XFree latest, R version 1.9.1 home-compiled. -----Original Message----- From: Prof Brian Ripley [mailto:ripley at stats.ox.ac.uk] Sent: ??????, 16 ??????????? 2004 16:27 To: Christos Rodopoulos Cc: 'R-help at stat.math.ethz.ch' Subject: Re: FW: [R] How do I insert a newline in my title in a plot? On Thu, 16 Sep 2004,

Hi! I would like to suggest to make it possible, in one way or another, to get meaningful contrast names when using contr.sum(). Currently, when using contr.treatment(), one gets factor levels as contrast names; but when using contr.sum(), contrasts are merely numbered, which is not practical and can lead to mistakes (see code at the end of this message). This issue was discussed quickly in 2005

There's more to it than that (which was already fixed in R-devel). The internal code expects there to be columns in the model frame. I have already fixed this in R-devel (by faking an unused column). On Tue, 25 Sep 2001 murdoch@stats.uwo.ca wrote: > On Tue, 25 Sep 2001 12:27:27 GMT, Jorge Luis Ojeda Cabrera > <jojeda@posta.unizar.es> wrote in message >

Dear R-helpers, In the case of two categorical factors, say a and b, once I have fixed the constrasts, the model matrix is set according to these contrasts with "lm", and the t-tests for the significance of the parameters provided by "summary" indeed concern the comparison of the model with each submodel obtained by removing the corresponding column of the model matrix.

On Thu, Feb 21, 2019 at 7:49 AM Fox, John <jfox at mcmaster.ca> wrote: > > Dear Ben, > > Perhaps I'm missing the point, but contrasts.arg is documented to be a list. From ?model.matrix: "contrasts.arg: A list, whose entries are values (numeric matrices or character strings naming functions) to be used as replacement values for the contrasts replacement function and whose

> From: "Alan T. Arnholt" <arnholt at math.appstate.edu> > To: Bill Venables <William.Venables at cmis.CSIRO.AU> > Cc: r-help at stat.math.ethz.ch, arnholt at math.appstate.edu > Subject: Re: [R] Lack of Fit test > Date: Wed, 23 Feb 2000 09:40:21 -0500 (EST) > X-Authentication: none > > > I guess my question was not adequately stated when I sent

On Tue, 7 Mar 2000, Martin Maechler wrote: > >>>>> "BDR" == Prof Brian D Ripley <ripley@stats.ox.ac.uk> writes: > > BDR> On Tue, 7 Mar 2000, Trenkler, Dietrich wrote: > >> I think I've discovered what went wrong. > >> > >> My workspace included a function wilcox.test formerly copied from > >>

Dear experts: Is it possible to create a new function based on stats:::model.matrix.default so that an alternative factor coding is used when the function is called instead of the default factor coding? Basically, I'd like to reproduce the results in 'mat' below, without having to explicitly specify my desired factor coding (identity matrices) in the 'contrasts.arg'. dd

Dear Martin and Ben, I agree that a warning is a good idea (and perhaps that wasn't clear in my response to Ben's post). Also, it would be nice to correct the omission in the help file, which as far as I could see doesn't mention that a contrast-generating function (as opposed to its quoted name) can be an element of the contrasts.arg list. Best, John > -----Original

Dear R-devel list members, I'd like to suggest a more flexible procedure for generating contrast names. I apologise for a relatively long message -- I want my proposal to be clear. I've never liked the current approach. For example, the names generated by contr.treatment paste factor to level names with no separation between the two; contr.sum simply numbers contrasts (I recall an

Hi, I need to build a function to generate one column for each level of a factor in the model matrix created on an arbitrary formula (instead of using the available contrasts options such as contr.treatment, contr.SAS, etc). My approach to this was first to use the built-in function for contr.treatment but changing the default value of the contrasts argument to FALSE (I named this function

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I am using RW 1.2.3. on an IBM PC 300GL. Using the data bp.dat which accompanies Helen Brown and Robin Prescott 1999 Applied Mixed Models in Medicine. Statistics in Practice. John Wiley & Sons, Inc., New York, NY, USA which is also found at www.med.ed.ac.uk/phs/mixed. The data file was opened and initialized with > dat <- read.table("bp.dat") >

As far as I can see sys.on.exit() does not work. The following will give a non-null result in S, and seems about the simplest possible usage. test <- function() { on.exit(print(1)) ex <- sys.on.exit() str(ex) cat("exiting...\n") } > test() NULL exiting... [1] 1 Looking at the code suggests that on.exit is installing the code in a different context from the one

Dear Ben, Perhaps I'm missing the point, but contrasts.arg is documented to be a list. From ?model.matrix: "contrasts.arg: A list, whose entries are values (numeric matrices or character strings naming functions) to be used as replacement values for the contrasts replacement function and whose names are the names of columns of data containing factors." This isn't entirely

For ordered factor the natural contrast coding would be to parametrize by the succsessive differences between levels, which does not assume equal spacing of factor levels as does the polynomial contrasts (implicitly at least). This requires the contr.cum, which could be: contr.cum <- function (n, contrasts = TRUE) { if (is.numeric(n) && length(n) == 1) levs <- 1:n