[R] What does it mean to be "masked from data" when attaching? (Newbie question)
Dimitrios Rizopoulos
Dimitris.Rizopoulos at med.kuleuven.be
Sat May 13 21:31:32 CEST 2006
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]]
>
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