[Rd] strange bahaviour of predict.lm

[Rui Barradas]

Hello,

I'm glad that it worked.
Two things:

1. Please, click reply all to keep this threaded.
2. The question should have belonged to r-help using r-project.org, not to 
r-devel using r-project.org.

Rui Barradas

Às 07:10 de 17/03/20, Moshe Olshansky escreveu:
> It works, thank you!
> 
> On Tuesday, 17 March 2020, 5:47:05 pm AEDT, Rui Barradas 
> <ruipbarradas using sapo.pt> wrote:
> 
> 
> Hello,
> 
> The problem seems to be that A is a matrix. The following solves the error.
> 
> # create A and b as in your code then run
> A <- as.data.frame(A)
> df1 <- cbind(A, b)
> reg <- lm(b ~ ., df1)
> 
> # etc
> 
> 
> Hope this helps,
> 
> Rui Barradas
> 
> Às 04:36 de 17/03/20, Moshe Olshansky via R-devel escreveu:
>  > Hello,
>  > Below is my code:
>  >> A <- matrix(rnorm(10*3),ncol=3)
>  >> b <- runif(10)
>  >> reg <- lm(b ~ A)
>  >> A1 <- matrix(rnorm(5*3),ncol=3)
>  >> A1 <- as.data.frame(A1)
>  >> b1 <- predict(reg,A1)
>  > Warning message:
>  > 'newdata' had 5 rows but variables found have 10 rows
>  >
>  >    And instead of being an array of length 5, b1 is of length 10 and 
> is identical to reg$fitted.values
>  > I think that it should not be like this.
>  > Let me note that for lm I do not care about this as much since I can 
> use reg$coefficients, but unfortunately this behaviour is "inherited" by 
> other methods. When I am trying to fit a regression tree, predicting 
> from the object without using 'predict' method is less trivial.
>  > Thank you,Moshe.
>  > P.S. just in case:> sessionInfo()
>  > R version 3.6.2 (2019-12-12)
>  > Platform: x86_64-pc-linux-gnu (64-bit)
>  > Running under: Linux Mint 19.1
>  >
>  > Matrix products: default
>  > BLAS:   /usr/lib/x86_64-linux-gnu/blas/libblas.so.3.7.1
>  > LAPACK: /usr/lib/x86_64-linux-gnu/lapack/liblapack.so.3.7.1
>  >
>  > locale:
>  > [1] C
>  >
>  > attached base packages:
>  > [1] stats     graphics  grDevices utils     datasets  methods   base
>  >
>  > loaded via a namespace (and not attached):
>  > [1] compiler_3.6.2 tools_3.6.2
> 
>  >
>  >
>  >
>  >
>  >
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>  >
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