Re: [Rd] Wish R Core had a standard format (or generic function) for "newdata" objects

From: Paul Johnson <>
Date: Wed, 27 Apr 2011 11:20:28 -0500

On Tue, Apr 26, 2011 at 7:39 PM, Duncan Murdoch <> wrote:

> If you don't like the way this was done in my three lines above, or by Frank
> Harrell, or the Zelig group, or John Fox, why don't you do it yourself, and
> get it right this time?  It's pretty rude to complain about things that
> others have given you for free, and demand they do it better.
> Duncan Murdoch

I offer sincere apology for sounding that way. I'm not attacking anybody. I'm just talking, asking don't you agree this were standardized. And you disagree, and I respect that since you are actually doing the work.

>From a "lowly user's point of view", I wish "you experts" out there
would tell us one way to do this, we could follow your example.

When there's a regression model fitted with 20 variables in it, and half of them are numeric, 4 are unordered factors, 3 are ordinal factors, and what not, then this is a hard problem for many of us ordinary users. Or it is tedious. They want "keep everything fixed," except one variable that takes on different specified values. And they want to do that for every variable, one at a time.

Stata has made this easy for many models, R could as well, if we coalesced on a more-or-less standard way to create newdata objects for predict.

But, in the end, I agree with your sentiment. I just have to do this, show you it is handy. I think Zelig's setx has it about right, I'll pursue that strategy.


Paul E. Johnson
Professor, Political Science
1541 Lilac Lane, Room 504
University of Kansas

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