R help - Jun 2007 - question about formula for lm

Dear all;

Is there any way to make this to work?:

.x<-rnorm(50,10,3)
.y<-.x+rnorm(50,0,1)

X<-data.frame(.x,.y)
colnames(X)<-c("Xvar","Yvar")

Ytext<-"Yvar"

lm(Ytext~Xvar,data=X) # doesn't run

lm(Yvar~Xvar,data=X) # does run

The main idea is to use Ytext as input in a function, so you just type
"Yvar" and the model should fit....
Also, I need to avoid the expression X$Yvar~X$Xvar

Thanks for any idea

PM

Why not using:

lm(X[[Ytext]]~Xvar,data=X)


ThPe


Pedro Mardones wrote:
> Dear all;
> 
> Is there any way to make this to work?:
> 
> .x<-rnorm(50,10,3)
> .y<-.x+rnorm(50,0,1)
> 
> X<-data.frame(.x,.y)
> colnames(X)<-c("Xvar","Yvar")
> 
> Ytext<-"Yvar"
> 
> lm(Ytext~Xvar,data=X) # doesn't run
> 
> lm(Yvar~Xvar,data=X) # does run
> 
> The main idea is to use Ytext as input in a function, so you just type
> "Yvar" and the model should fit....
> Also, I need to avoid the expression X$Yvar~X$Xvar
> 
> Thanks for any idea
> 
> PM
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

First check the value of Ytext. 

Try 
Ytext <- X$Yvar

--- Pedro Mardones <mardones.p at gmail.com> wrote:
> Dear all;
> 
> Is there any way to make this to work?:
> 
> .x<-rnorm(50,10,3)
> .y<-.x+rnorm(50,0,1)
> 
> X<-data.frame(.x,.y)
> colnames(X)<-c("Xvar","Yvar")
> 
> Ytext<-"Yvar"
> 
> lm(Ytext~Xvar,data=X) # doesn't run
> 
> lm(Yvar~Xvar,data=X) # does run
> 
> The main idea is to use Ytext as input in a
> function, so you just type
> "Yvar" and the model should fit....
> Also, I need to avoid the expression X$Yvar~X$Xvar
> 
> Thanks for any idea
> 
> PM
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained,
> reproducible code.
>

Try:
> lm( formula( paste( Ytext, '~ Xvar' ) ), data=X)
-- 
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at intermountainmail.org
(801) 408-8111
 
 
> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Pedro Mardones
> Sent: Thursday, June 14, 2007 1:14 PM
> To: R-help at stat.math.ethz.ch
> Subject: [R] question about formula for lm
> 
> Dear all;
> 
> Is there any way to make this to work?:
> 
> .x<-rnorm(50,10,3)
> .y<-.x+rnorm(50,0,1)
> 
> X<-data.frame(.x,.y)
> colnames(X)<-c("Xvar","Yvar")
> 
> Ytext<-"Yvar"
> 
> lm(Ytext~Xvar,data=X) # doesn't run
> 
> lm(Yvar~Xvar,data=X) # does run
> 
> The main idea is to use Ytext as input in a function, so you 
> just type "Yvar" and the model should fit....
> Also, I need to avoid the expression X$Yvar~X$Xvar
> 
> Thanks for any idea
> 
> PM
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

A couple of easy ways are to create the calling sequence as a call or
character string and then evaluate it:

eval(bquote(lm(.(as.name(Ytext)) ~ Xvar, X)))

eval(parse(text = paste("lm(", Ytext, "~ Xvar, X)")))

Note that these solutions both have the advantage over some of the prior
solutions that the output from print.lm shows which variable was actually used
after Call:

> eval(bquote(lm(.(as.name(Ytext)) ~ Xvar, X)))
Call:
lm(formula = Yvar ~ Xvar, data = X)  <--- This line comes out meaningfully!!!

Coefficients:
(Intercept)         Xvar
     0.3300       0.9729


On 6/14/07, Pedro Mardones <mardones.p at gmail.com>
wrote:
> Dear all;
>
> Is there any way to make this to work?:
>
> .x<-rnorm(50,10,3)
> .y<-.x+rnorm(50,0,1)
>
> X<-data.frame(.x,.y)
> colnames(X)<-c("Xvar","Yvar")
>
> Ytext<-"Yvar"
>
> lm(Ytext~Xvar,data=X) # doesn't run
>
> lm(Yvar~Xvar,data=X) # does run
>
> The main idea is to use Ytext as input in a function, so you just type
> "Yvar" and the model should fit....
> Also, I need to avoid the expression X$Yvar~X$Xvar
>
> Thanks for any idea
>
> PM
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>