[R] Converting data frame to array?

[Spencer Graves]

      stepAIC in library(MASS) or "step"? 

      hope this helps.  spencer graves

TAPO (Thomas Agersten Poulsen) wrote:

>Dear John,
>
>	Thank you for your helpful answer. I was obviously being stupid,
>as I have, as you point out, more predictors than observations.
>
>	What I was hoping to get was some sort of an "explaining linear
>combination" of my predictors: which predictors are important for the
>results I see (if any) and which are irrelevant. 
>
>	Any hints on how to achieve that?
>	
>Cheers
>Thomas
>
>-----Original Message-----
>From: John Fox [mailto:jfox at mcmaster.ca] 
>Sent: 29. maj 2004 01:24
>To: TAPO (Thomas Agersten Poulsen)
>Cc: r-help at stat.math.ethz.ch
>Subject: RE: [R] Converting data frame to array?
>
>
>Dear Thomas,
>
>In fact, the more common way to fit a linear regression in R is to use
>variables in a data frame (or list) along with a model formula
>specifying the model. All of this is explained in the Introduction to R
>manual that is distributed with R: see, in particular, Sec. 6.3 on data
>frames, Sec. 7 on reading data from files, and Sec. 11 on statistical
>models.
>
>Given two data frames, say d1 and d2, the first containing, e.g.,
>observations on variables x1 and x2 and the second on y, one could do
>lm(y ~ x1 + x2, data=c(x1, x2)) or lm(y ~ x1 + x2, data=data.frame(x1,
>x2)). 
>
>That said, it's not altogether clear to me what it is that you're trying
>to do. Are there 10 observations on 300 variables in the first data
>frame, constituting the predictors, and 10 observations on 1 variable in
>the second data frame, constituting the response? If so, you have many
>more predictors than observations, and it's not reasonable to perform a
>regression. Of course, I may not have this straight.
>
>I hope this helps,
> John
>
>  
>
>>-----Original Message-----
>>From: r-help-bounces at stat.math.ethz.ch
>>[mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of TAPO 
>>(Thomas Agersten Poulsen)
>>Sent: Friday, May 28, 2004 2:11 PM
>>To: r-help at stat.math.ethz.ch
>>Subject: [R] Converting data frame to array?
>>
>>Dear List,
>>
>>	Please bear with a poor newbee, who might be doing
>>everything backwards (I was brought up in pure math).
>>
>>	I want to make a simple multi-linear regression on a
>>set of data. I did some expreiments, and if X is a 4 by 2 
>>array and Y is a 4 by
>>1 array, I can do a linear regression by lm(y~x). 
>>
>>	Now I have a tab-delimited text file with 10 rows of
>>300 measurements and an other file with 10 rows of one value 
>>each. When I read in those files using read.delim(), I get 
>>data frames, and apparently I can no longer do the 
>>multi-linear regression.
>>
>>	Is there a way to convert the data frames into arrays,
>>or am I going the wrong way about this?
>>
>>Sincerely
>>Thomas Poulsen
>>
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>>
>
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