R help - May 2006 - What does it mean to be "masked from data" when attaching? (Newbie question)

I have several data frames, each with six variables and several hundred
cases broken out from a larger dataframe by eleven values of a factor
called "Division".  I have to perform the same analysis on each one. 
I
would like to do it by creating a data frame called data2 eleven times,
once with data corresponding to each value of the factor, and performing
the same analysis on each of the eleven values of data2.  However, when
I assign to data2 the value of one of my data frames, e.g. data2 <-
Florida, and then attach data2, I get the warning 

 

        The following object(s) are masked from data2 ( position 3 ) :

         Day Division SchedNo Spent TimeEnter TimeInStr 

        The following object(s) are masked from Alb3 :

         Day Division SchedNo Spent TimeEnter TimeInStr 

        The following object(s) are masked from data2 ( position 5 ) :

         Day Division SchedNo Spent TimeEnter TimeInStr 

 

I am having trouble finding an explanation of these messages, what the
"position" refers to, and what it means to be "masked."  Can
someone
steer me to an online explanation?

 

And by the way, one of the analyses I have to perform is simply to
tabulate the days of the week that occur in variable "Day" by using
table(Day) which gives, for example,

 

Day

 Fri  Mon  Sat  Sun Thur  Tue  Wed 

 173  191  111   92  188  218  187

 

What is the proper syntax for doing that by levels of a factor within
the large data frame containing all eleven factors?  I have
unsuccessfully tried to use "by".

 

Thanks,

 

Ben F.


	[[alternative HTML version deleted]]

the problem you get comes from the fact that you attach the 
data.frame, e.g., it can be re-produced by:

x1 <- rnorm(30)
dat <- data.frame(x1 = rnorm(30))
attach(dat)

look at ?attach for more details; you could consider with() as an 
alternative.

I hope it helps.

Best,
Dimitris


-- 
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/
     http://www.student.kuleuven.be/~m0390867/dimitris.htm


Quoting Ben Fairbank <BEN at ssanet.com>:
> I have several data frames, each with six variables and several
> hundred
> cases broken out from a larger dataframe by eleven values of a
> factor
> called "Division".  I have to perform the same analysis on each
one.
> I
> would like to do it by creating a data frame called data2 eleven
> times,
> once with data corresponding to each value of the factor, and
> performing
> the same analysis on each of the eleven values of data2.  However,
> when
> I assign to data2 the value of one of my data frames, e.g. data2 <-
> Florida, and then attach data2, I get the warning 
> 
>  
> 
>         The following object(s) are masked from data2 ( position 3 )
> :
> 
>          Day Division SchedNo Spent TimeEnter TimeInStr 
> 
>         The following object(s) are masked from Alb3 :
> 
>          Day Division SchedNo Spent TimeEnter TimeInStr 
> 
>         The following object(s) are masked from data2 ( position 5 )
> :
> 
>          Day Division SchedNo Spent TimeEnter TimeInStr 
> 
>  
> 
> I am having trouble finding an explanation of these messages, what
> the
> "position" refers to, and what it means to be "masked."
Can someone
> steer me to an online explanation?
> 
>  
> 
> And by the way, one of the analyses I have to perform is simply to
> tabulate the days of the week that occur in variable "Day" by
using
> table(Day) which gives, for example,
> 
>  
> 
> Day
> 
>  Fri  Mon  Sat  Sun Thur  Tue  Wed 
> 
>  173  191  111   92  188  218  187
> 
>  
> 
> What is the proper syntax for doing that by levels of a factor
> within
> the large data frame containing all eleven factors?  I have
> unsuccessfully tried to use "by".
> 
>  
> 
> Thanks,
> 
>  
> 
> Ben F.
> 
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> 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
> 
> 

Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm

On 5/13/2006 2:52 PM, Ben Fairbank wrote:
> I have several data frames, each with six variables and several hundred
> cases broken out from a larger dataframe by eleven values of a factor
> called "Division".  I have to perform the same analysis on each
one.  I
> would like to do it by creating a data frame called data2 eleven times,
> once with data corresponding to each value of the factor, and performing
> the same analysis on each of the eleven values of data2.  However, when
> I assign to data2 the value of one of my data frames, e.g. data2 <-
> Florida, and then attach data2, I get the warning 
> 
>  
> 
>         The following object(s) are masked from data2 ( position 3 ) :
> 
>          Day Division SchedNo Spent TimeEnter TimeInStr 
> 
>         The following object(s) are masked from Alb3 :
> 
>          Day Division SchedNo Spent TimeEnter TimeInStr 
> 
>         The following object(s) are masked from data2 ( position 5 ) :
> 
>          Day Division SchedNo Spent TimeEnter TimeInStr 
> 
>  
> 
> I am having trouble finding an explanation of these messages, what the
> "position" refers to, and what it means to be "masked."
Can someone
> steer me to an online explanation?
It is the position in the search list.  See search() for the complete list.

It sounds as though you are attaching things, but not detaching them: 
and R is warning that the new attach is hiding something from the 
previous one.

The Introduction to R manual discusses this in the "Data frames"
section
of the "Lists and data frames" chapter.

Duncan Murdoch
> 
>  
> 
> And by the way, one of the analyses I have to perform is simply to
> tabulate the days of the week that occur in variable "Day" by
using
> table(Day) which gives, for example,
> 
>  
> 
> Day
> 
>  Fri  Mon  Sat  Sun Thur  Tue  Wed 
> 
>  173  191  111   92  188  218  187
> 
>  
> 
> What is the proper syntax for doing that by levels of a factor within
> the large data frame containing all eleven factors?  I have
> unsuccessfully tried to use "by".
> 
>  
> 
> Thanks,
> 
>  
> 
> Ben F.
> 
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> 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