Converting data frame to array?

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