Programcode and data in the same textfile

-----Original Message-----
From: Torsten Hothorn [mailto:Torsten.Hothorn at rzmail.uni-erlangen.de]
Sent: 12 June 2003 14:00
To: Ernst Hansen
Cc: r-help at stat.math.ethz.ch
Subject: Re: [R] Programcode and data in the same textfile

I have the following problem.  It is not of earthshaking importance,
but still I have spent a considerable amount of time thinking about
it.

PROBLEM: Is there any way I can have a single textfile that contains
both

  a) data

  b) programcode

The program should act on the data, if the textfile is source()'ed
into R.


BOUNDARY CONDITION: I want the data written in the textfile 

in exactly

the same format as I would use, if I had data in a separate 

textfile,

to be read by read.table().  That is, with 'horizontal 

inhomogeneity'

and 'vertical homogeneity' in the type of entries.  I want to write
something like

      Sex    Respons
      Male   1
      Male   2
      Female 3
      Female 4

something like

  tmpfilename <- tempfile()
  tmpfile <- file(tmpfilename, "w")
  cat(

      ### here comes my data

      "Sex    Respons",
      "Male   1",
      "Male   2",
      "Female 3",
      "Female 4",

      ### end of data input

      file = tmpfile, sep="\n")
  close(tmpfile)
  read.table(tmpfilename, header = TRUE)


best,

Torsten

In effect, I am asking if there is some way I can convince
read.table(), that the data is contained in the following n lines of
text.


ILLEGAL SOLUTIONS:
I know I can simulate the behaviour by reading the columns of the
dataframe one by one, and using data.frame() to glue them together.
Like in

    data.frame(Sex = c('Male', 'Male', 'Female', 'Female'),
               Respons = c(1, 2, 3, 4))

I do not like this solution, because it represents the data in a
"transposed" way in the textfile, and this transposition makes the
structure of the dataframe less transparent - at least to me. It
becomes even less comprehensible if the Sex-factor above is written
with the help of rep() or gl() or the like.

I know I can make read.table() read from stdin, so I could type the
dataframe at the prompt.  That is against the spirit of the problem,
as I describe below.


I know I can make read.table() do the job, if I split the 

data and the

programcode in to different files.  But as the purpose of 

the exercise

is to distribute the data and the code to other people, splitting
into several files is a complication.


MOTIVATION: I frequently find myself distributing small 

chunks of code

to my students, along with data on which the code can work.

As an example, I might want to demonstrate how model.matrix() treats
interactions, in a certain setting.  For that I need a 

dataframe that

is complex enough to exhibit the behaviour I want, but 

still so small

that the model.matrix is easily understood.  So I make such a
dataframe.

I am trying to distribute this dataframe along with my 

code, in a way

that is as simple as possible to USE for the students (hence the
one-file boundary condition) and to READ (hence the 

non-transposition

boundary condition).



Does anybody have any ideas?


Ernst Hansen
Department of Statistics
University of Copenhagen