[R] Problem with the step() function

[ripley@stats.ox.ac.uk]

Use R-devel, where this has been changed and your example works.

On Mon, 24 Mar 2003, Luis Torgo wrote:

> Dear all,
> I'm having some problems with using the step() function inside another 
> function. I think it is an environment problem but I do not know how to 
> overcome it. Any suggestions are appreciated. 
> 
> I've prepared a simple example to illustrate my problem:
> 
> > library(MASS)
> > data(Boston)
> > my.fun <- function(dataset) {
> +   l <- lm(medv ~ .,data=dataset)
> +   final.l <- step(l)
> + }
> > model <- my.fun(Boston)
> Start:  AIC= 1589.64 
>  medv ~ crim + zn + indus + chas + nox + rm + age + dis + rad +  
>     tax + ptratio + black + lstat 
> 
>           Df Sum of Sq     RSS     AIC
> - age      1       0.1 11078.8  1587.6
> - indus    1       2.5 11081.3  1587.8
> <none>                 11078.8  1589.6
> - chas     1     219.0 11297.8  1597.5
> - tax      1     242.3 11321.0  1598.6
> - crim     1     243.2 11322.0  1598.6
> - zn       1     257.5 11336.3  1599.3
> - black    1     270.6 11349.4  1599.9
> - rad      1     479.2 11557.9  1609.1
> - nox      1     487.2 11565.9  1609.4
> - ptratio  1    1194.2 12273.0  1639.4
> - dis      1    1232.4 12311.2  1641.0
> - rm       1    1871.3 12950.1  1666.6
> - lstat    1    2410.8 13489.6  1687.3
> Error in model.frame.default(formula = medv ~ crim + zn + indus + chas +  : 
> 	Object "dataset" not found
> 
> Apparently the step() function is not able to find the "dataset" object which 
> is created inside the my.fun() function.
> 
> My system information:
> > R.version
>          _                
> platform i686-pc-linux-gnu
> arch     i686             
> os       linux-gnu        
> system   i686, linux-gnu  
> status                    
> major    1                
> minor    6.1              
> year     2002             
> month    11               
> day      01               
> language R
> 
> Thank you for any hints.
> 
> 

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595