[R] Getting lm() to work with a matrix

[Berwin A Turlach]

G'day Luc,

On Wed, 20 May 2009 09:58:41 -0400
Luc Villandre <villandl at dms.umontreal.ca> wrote:

> MikSmith wrote:
> > [...]

> Indeed, functions like /lm()/ require the object fed to the /data/ 
> argument to be either [...]

But the data argument is optional and does not need to be specified.

> In your situation, I suggest you typecast your matrix into a data
> frame using /as.data.frame()/.  [...]

My guess is that he is already working with a data frame and does not
work with matrices, otherwise he should not have encountered problems:

R> response <- matrix(rnorm(120), ncol=4)
R> spectra.spec <- matrix(rnorm(900), ncol=30)
R> spectra.lm <- lm(response[,3]~spectra.spec[,2:20])
R> spectra.lm

Call:
lm(formula = response[, 3] ~ spectra.spec[, 2:20])

Coefficients:
           (Intercept)   spectra.spec[, 2:20]1  
              -0.48404                 0.42503  
 spectra.spec[, 2:20]2   spectra.spec[, 2:20]3  
              -0.08955                -0.27605  
 spectra.spec[, 2:20]4   spectra.spec[, 2:20]5  
              -0.16832                -0.14107  
 spectra.spec[, 2:20]6   spectra.spec[, 2:20]7  
              -0.47009                -0.23672  
 spectra.spec[, 2:20]8   spectra.spec[, 2:20]9  
               0.12920                 0.23306  
spectra.spec[, 2:20]10  spectra.spec[, 2:20]11  
              -0.28586                 0.03579  
spectra.spec[, 2:20]12  spectra.spec[, 2:20]13  
               0.10676                -0.34407  
spectra.spec[, 2:20]14  spectra.spec[, 2:20]15  
               0.20253                -0.17259  
spectra.spec[, 2:20]16  spectra.spec[, 2:20]17  
               0.19765                 0.40705  
spectra.spec[, 2:20]18  spectra.spec[, 2:20]19  
              -0.12448                -0.17149  

Cheers,

	Berwin