Like, Was: Re: [R] rbind'ing empty rows in dataframes in 1.4.1 versus 1.5.0

[Don MacQueen]

More than once, including in a project I'm currently working on, I 
could really use such a function. If you don't mind I'll make a local 
copy and use it until it hopefully gets into R. Want me to start a 
help page?

Good that it preserves mode and data.class, including "AsIs".

-Don

At 11:19 PM +0200 5/6/02, Peter Dalgaard BSA wrote:
>"David Kane  <David Kane" <a296180 at mica.fmr.com> writes:
>
>>  > x <- data.frame(a = letters[1:3], b = 1:3)
>>  > x
>>    a b
>>  1 a 1
>>  2 b 2
>>  3 c 3
>>  > x[4,]
>>      a  b
>>  NA NA NA
>>  > rbind(x, x[4,])
>>      a  b
>>  1   a  1
>>  2   b  2
>>  3   c  3
>>  NA NA NA
>....
>>  This does not work in 1.5.0
>....
>
>Brian fixed this for 1.5.1. However, the whole idea helped me with
>something that has been bugging me for years:
>
>When you want to predict on new data
>
>foo <- lm(formula, data=foe)
>predict(foo, newdata=fie)
>
>you have to be careful that foe and fie  are compatible, all factors
>have the same level set, and so forth. This can be quite a pain, so I
>wanted a "like" function as in
>
>fie <- like(foe, sex="F", age=20:25, smoke="1-7")
>
>but only after seeing the above way of making "blank" rows, it dawned
>upon me that such rows have exactly the properties I wanted.
>Elaborating a little, I got
>
>like <- function(X,...){
>     l <- list(...)
>     n <- max(sapply(l, length))
>     X <- X[rep(as.numeric(NA),n),]
>     row.names(X) <- seq(length=n)
>     for (nm in names(l)) X[[nm]][] <- l[[nm]]
>     X
>}
>
>A six-liner! Neat, eh? Probably has a good chance of making it into
>1.6 once I get around to writing a help page.
>
>--
>    O__  ---- Peter Dalgaard             Blegdamsvej 3 
>   c/ /'_ --- Dept. of Biostatistics     2200 Cph. N  
>  (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
>~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
>
>
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-- 
--------------------------------------
Don MacQueen
Environmental Protection Department
Lawrence Livermore National Laboratory
Livermore, CA, USA
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