R help - Aug 2003 - lm(), na.exclude and predict()

I'm trying to get predict.lm() to return an NA for each NA row in it's
input vector, so the output is the same length as the input.

I thought that using na.action=na.exclude with lm() would do that. But
apparently not ??

df <- data.frame(x=c(NA,1,2,3,NA),y=c(0,2,3,4,0))
tl <- lm(y~x,df,na.action=na.exclude)
predict.lm(tl,data.frame(x=c(2.5,NA,3,4,5)))
  1   3   4   5
3.5 4.0 5.0 6.0

Any suggestions?

Bruce

On Fri, 8 Aug 2003, Nurnberg-LaZerte wrote:
> I'm trying to get predict.lm() to return an NA for each NA row in
it's
> input vector, so the output is the same length as the input.
Don't call predict.lm directly, please.  Use predict().
> I thought that using na.action=na.exclude with lm() would do that. But
> apparently not ??
That tells R to fit with na.exclude, not to predict with na.exclude.
Prediction uses a separate setting of na.action.
> df <- data.frame(x=c(NA,1,2,3,NA),y=c(0,2,3,4,0))
> tl <- lm(y~x,df,na.action=na.exclude)
> predict.lm(tl,data.frame(x=c(2.5,NA,3,4,5)))
>   1   3   4   5
> 3.5 4.0 5.0 6.0
> 
> Any suggestions?
In R-devel
> predict(tl,data.frame(x=c(2.5,NA,3,4,5)))
  1   2   3   4   5 
3.5  NA 4.0 5.0 6.0 

since there is a na.action argument to the predict method defaulting to 
na.pass.

In R 1.7.1
> op <- options(na.action=na.pass)
> predict(tl,data.frame(x=c(2.5,NA,3,4,5)))
  1   2   3   4   5 
3.5  NA 4.0 5.0 6.0 
> par(op)
as the session-wide default is used.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
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