R help - Jul 2001 - style question: returning multiple arguments - structure orlist

I see Thomas has already nailed this one, so it becomes a non-issue.
Nevertheless I feel moved to say I think the idea would have been a step in
the wrong direction in the first place.  It comes from a desire to make R
behave "a bit more like matlab" and that is ultimately unhelpful.

Having tried to teach generations of students how to use the system (S-PLUS,
but it could equally well have been R) I can say the most difficult people
to teach it to are those you have to "convert" from a long history of
expertise in another system.  Trying to make R behave like the previous
system (SAS, Stata, SPSS, Matlab, APL, ....), as they are invariably
determined to do, is ultimately futile, but you, the teacher, find yourself
doing all sorts of hand-stands and cartwheels to meet these people half-way.

It doesn't work.  Trust me.  In the end it *really* *doesn't* *work*.
Seriously.

I'm not sure how we can best help these people, either, but I'm working
on
it.  It comes as a dreadful shock for them to find that R is not just SAS,
or Matlab, or APL, or... in some foreign notation but a genuinely different
system.  They have real trouble expanding their mental outlook just enough
to handle the fact that such a thing is even possible.

In Adelaide where I taught with S-PLUS for about a decade I had no real
problems in getting the students on board.  (Some, like David Smith, even
went on to have distinguished careers in the game.)  But I got nowhere with
my fellow staff members, some of whom just never got over Matlab, or SAS, or
... 

Sigh.

Bill Venables.





-----Original Message-----
From: Peter Dalgaard BSA [mailto:p.dalgaard at biostat.ku.dk]
Sent: Sunday, 29 July 2001 7:24 AM
To: vogels at cmu.edu
Cc: rhelp
Subject: Re: [R] style question: returning multiple arguments -
structure orlist


"Thomas J Vogels" <tov at ece.cmu.edu> writes:
> Hi,
> 
> you also have the option of "throwing out" the third result by
setting it
to
> NULL (taking your LIST option)?
> 
> > f <- function() {
> >   ...
> >   list(x=x,y=y,z=z)
> > }
> > res <- f()
> > names(jj)
> [1] "x" "y" "z"
> > res$z <- NULL
> > names(res)
> [1] "x" "y"
> 
> and then work with res (res$x and res$y)?
A little summer exercise: Can one write a list assignment function,
i.e. "list<-" so that

list(a,b,c) <- f()

would be equivalent to

r <- f()
a <- r[[1]]
b <- r[[2]]
c <- r[[3]]

Even better, do something useful with named list elements. (And what
are the odds of finding that this is really an exercise hidden
somewhere in a book by Venables and Ripley?)

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
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"Venables, Bill (CMIS, Cleveland)" <Bill.Venables at
CMIS.CSIRO.AU> writes:
> I see Thomas has already nailed this one, so it becomes a non-issue.
> Nevertheless I feel moved to say I think the idea would have been a step in
> the wrong direction in the first place.  It comes from a desire to make R
> behave "a bit more like matlab" and that is ultimately unhelpful.
> 
> Having tried to teach generations of students how to use the system
(S-PLUS,
> but it could equally well have been R) I can say the most difficult people
> to teach it to are those you have to "convert" from a long
history of
> expertise in another system.  Trying to make R behave like the previous
> system (SAS, Stata, SPSS, Matlab, APL, ....), as they are invariably
> determined to do, is ultimately futile, but you, the teacher, find yourself
> doing all sorts of hand-stands and cartwheels to meet these people
half-way.
> 
> It doesn't work.  Trust me.  In the end it *really* *doesn't*
*work*.
> Seriously.
> 
> I'm not sure how we can best help these people, either, but I'm
working on
> it.  It comes as a dreadful shock for them to find that R is not just SAS,
> or Matlab, or APL, or... in some foreign notation but a genuinely different
> system.  They have real trouble expanding their mental outlook just enough
> to handle the fact that such a thing is even possible.
> 
> In Adelaide where I taught with S-PLUS for about a decade I had no real
> problems in getting the students on board.  (Some, like David Smith, even
> went on to have distinguished careers in the game.)  But I got nowhere with
> my fellow staff members, some of whom just never got over Matlab, or SAS,
or
> ... 
The counterpoint is that I often find it extremely instructive to try
and *make* R/S do some of the things it "can not do". This makes you
investigate some of the esoteric corners of the semantics, and
hopefully understand the whole thing a little bit better. It's not
invariably the case that you actually want to use the result of the
exercise, much less impose it on others.

I see the pedagogical problems we're facing largely as rooted in
"computational illiteracy". Basically, people have undeveloped
concepts of what computer languages are and what rules govern their
construction. 

I had the good fortune of starting at a point in time where the first
year of statistics coincided with the first year of Maths and Computer
Science. Later, this got changed to include a much less ambitious CS
course (for some good reasons, including the fact that it is useful to
teach statistics to first-year statistics students....) 

I only recently realized that this has become a straight
Pascal programming class, which the brighter students manage with
their left hand, but they learn nothing about general algorithmic
topics, parser theory, and formal program verification techniques
(actually, we didn't learn much about parsers and compilers either,
but at least we knew that they were there).

At the lower levels, people nowadays don't even realize that computer
languages exist, and expect everything to work like the Windows
desktop and characterize everything else as "DOS-like". 

As for the original challenge, I think you can actually get by with
overloading "[<-", leading to syntax of the form

LIST[a,b,c] <- f()

(which you most certainly would not want to inflict on standard R!)

LIST would want to be an object of class "foo" and
"[<-.foo" a
function that returns its first argument unchanged, and has its way
with the other arguments.

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at
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I too am troubled by the computer illiteracy of students
these days.  As an experiment this summer I am having
incoming students who don't know at least one computer
language work through the book "Beginning Programming
for Dummies" by Wallace Wang.  The book teaches programming
through the use of Qbasic (supplied on the CD-rom that
comes with the book) but introduces several other 
languages such as Java.  It appears to be a very good
book and has received good reviews.  My feeling is that
students who know any language such as basic, C, Python,
Perl, Fortran, Java will find it easier to learn S.
Many of my M.S. students have never even seen a DOS
prompt nor have they thought about a "variable".

There is a very good free interactive tutorial for learning
Tk/Tcl where students see explanations, example code,
and a window showing the results of running their own
code (http://www.msen.com/~clif/Tutor2b4.exe). I wish there 
were something like this for other languages, especially S.

-Frank


"Venables, Bill (CMIS, Cleveland)" wrote:
> 
> I see Thomas has already nailed this one, so it becomes a non-issue.
> Nevertheless I feel moved to say I think the idea would have been a step in
> the wrong direction in the first place.  It comes from a desire to make R
> behave "a bit more like matlab" and that is ultimately unhelpful.
> 
> Having tried to teach generations of students how to use the system
(S-PLUS,
> but it could equally well have been R) I can say the most difficult people
> to teach it to are those you have to "convert" from a long
history of
> expertise in another system.  Trying to make R behave like the previous
> system (SAS, Stata, SPSS, Matlab, APL, ....), as they are invariably
> determined to do, is ultimately futile, but you, the teacher, find yourself
> doing all sorts of hand-stands and cartwheels to meet these people
half-way.
> 
> It doesn't work.  Trust me.  In the end it *really* *doesn't*
*work*.
> Seriously.
> 
> I'm not sure how we can best help these people, either, but I'm
working on
> it.  It comes as a dreadful shock for them to find that R is not just SAS,
> or Matlab, or APL, or... in some foreign notation but a genuinely different
> system.  They have real trouble expanding their mental outlook just enough
> to handle the fact that such a thing is even possible.
> 
> In Adelaide where I taught with S-PLUS for about a decade I had no real
> problems in getting the students on board.  (Some, like David Smith, even
> went on to have distinguished careers in the game.)  But I got nowhere with
> my fellow staff members, some of whom just never got over Matlab, or SAS,
or
> ...
> 
> Sigh.
> 
> Bill Venables.
> 
> -----Original Message-----
> From: Peter Dalgaard BSA [mailto:p.dalgaard at biostat.ku.dk]
> Sent: Sunday, 29 July 2001 7:24 AM
> To: vogels at cmu.edu
> Cc: rhelp
> Subject: Re: [R] style question: returning multiple arguments -
> structure orlist
> 
> "Thomas J Vogels" <tov at ece.cmu.edu> writes:
> 
> > Hi,
> >
> > you also have the option of "throwing out" the third result
by setting it
> to
> > NULL (taking your LIST option)?
> >
> > > f <- function() {
> > >   ...
> > >   list(x=x,y=y,z=z)
> > > }
> > > res <- f()
> > > names(jj)
> > [1] "x" "y" "z"
> > > res$z <- NULL
> > > names(res)
> > [1] "x" "y"
> >
> > and then work with res (res$x and res$y)?
> 
> A little summer exercise: Can one write a list assignment function,
> i.e. "list<-" so that
> 
> list(a,b,c) <- f()
> 
> would be equivalent to
> 
> r <- f()
> a <- r[[1]]
> b <- r[[2]]
> c <- r[[3]]
> 
> Even better, do something useful with named list elements. (And what
> are the odds of finding that this is really an exercise hidden
> somewhere in a book by Venables and Ripley?)
> 
> --
>    O__  ---- Peter Dalgaard             Blegdamsvej 3
>   c/ /'_ --- Dept. of Biostatistics     2200 Cph. N
>  (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
> ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
>
-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.
> -.-
> r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
> Send "info", "help", or "[un]subscribe"
> (in the "body", not the subject !)  To: r-help-request at
stat.math.ethz.ch
>
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> _._
>
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> r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
> Send "info", "help", or "[un]subscribe"
> (in the "body", not the subject !)  To: r-help-request at
stat.math.ethz.ch
>
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._
-- 
Frank E Harrell Jr              Prof. of Biostatistics & Statistics
Div. of Biostatistics & Epidem. Dept. of Health Evaluation Sciences
U. Virginia School of Medicine  http://hesweb1.med.virginia.edu/biostat
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>From owner-r-help at stat.math.ethz.ch  Sun Jul 29 09:36:10 2001
>I too am troubled by the computer illiteracy of students
>these days.  As an experiment this summer I am having
>incoming students who don't know at least one computer
>language work through the book "Beginning Programming
>for Dummies" by Wallace Wang.
This sounds like a good book, but I want to make a pedagogical
point.  Although transfer of learning does occur, the last 100
years of research have tended to support the view that it is
incomplete and that it also works in both directions.  In my
youth, they tried to get me to learn Latin because it would "make
French easier."  (I refused, and learned German.)  The fact is
that learning French would make Latin easier, just as much as the
reverse.  Thus, if the target is S/R, teach S/R first.  It will
help students learn other languages just as much as the reverse.

Of course, the availability of good teaching materials is an
issue.  I plan to work on this in the fall, when I force the
students in our introductory graduate methods class to learn R,
both as a beginning cure for computer illiteracy and as a useful
tool in its own right - more useful for the average psychology
researcher, I think, than C or anything else.


Jonathan Baron, Professor of Psychology, University of Pennsylvania
Home page: http://www.sas.upenn.edu/~baron
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I quite agree with everything Peter says, of course and I don't think it
conflicts with anything I said at all - but it is one thing to explore he
possibilities of R/S by this kind of torture test and quite another to lead
people to think of them as a normal and reasonable uses of the language.

In similar vein I wish <<- had never been invented, as it makes an
esoteric
and dangerous feature of the language *seem* normal and reasonable.  If you
want to dumb down R/S into a macro language, this is the operator for you.

Bill.

-----Original Message-----
From: Peter Dalgaard BSA [mailto:p.dalgaard at biostat.ku.dk]
Sent: Sunday, 29 July 2001 9:45 PM
To: Venables, Bill (CMIS, Cleveland)
Cc: 'Peter Dalgaard BSA'; vogels at cmu.edu; rhelp; Thomas Lumley
(E-mail)
Subject: Re: [R] style question: returning multiple arguments -
structure orlist


"Venables, Bill (CMIS, Cleveland)" <Bill.Venables at
CMIS.CSIRO.AU> writes:
> I see Thomas has already nailed this one, so it becomes a non-issue.
> Nevertheless I feel moved to say I think the idea would have been a step
in
> the wrong direction in the first place.  It comes from a desire to make R
> behave "a bit more like matlab" and that is ultimately unhelpful.
> 
> Having tried to teach generations of students how to use the system
(S-PLUS,
> but it could equally well have been R) I can say the most difficult people
> to teach it to are those you have to "convert" from a long
history of
> expertise in another system.  Trying to make R behave like the previous
> system (SAS, Stata, SPSS, Matlab, APL, ....), as they are invariably
> determined to do, is ultimately futile, but you, the teacher, find
yourself
> doing all sorts of hand-stands and cartwheels to meet these people
half-way.
> 
> It doesn't work.  Trust me.  In the end it *really* *doesn't*
*work*.
> Seriously.
> 
> I'm not sure how we can best help these people, either, but I'm
working on
> it.  It comes as a dreadful shock for them to find that R is not just SAS,
> or Matlab, or APL, or... in some foreign notation but a genuinely
different
> system.  They have real trouble expanding their mental outlook just enough
> to handle the fact that such a thing is even possible.
> 
> In Adelaide where I taught with S-PLUS for about a decade I had no real
> problems in getting the students on board.  (Some, like David Smith, even
> went on to have distinguished careers in the game.)  But I got nowhere
with
> my fellow staff members, some of whom just never got over Matlab, or SAS,
or
> ... 
The counterpoint is that I often find it extremely instructive to try
and *make* R/S do some of the things it "can not do". This makes you
investigate some of the esoteric corners of the semantics, and
hopefully understand the whole thing a little bit better. It's not
invariably the case that you actually want to use the result of the
exercise, much less impose it on others.

I see the pedagogical problems we're facing largely as rooted in
"computational illiteracy". Basically, people have undeveloped
concepts of what computer languages are and what rules govern their
construction. 

I had the good fortune of starting at a point in time where the first
year of statistics coincided with the first year of Maths and Computer
Science. Later, this got changed to include a much less ambitious CS
course (for some good reasons, including the fact that it is useful to
teach statistics to first-year statistics students....) 

I only recently realized that this has become a straight
Pascal programming class, which the brighter students manage with
their left hand, but they learn nothing about general algorithmic
topics, parser theory, and formal program verification techniques
(actually, we didn't learn much about parsers and compilers either,
but at least we knew that they were there).

At the lower levels, people nowadays don't even realize that computer
languages exist, and expect everything to work like the Windows
desktop and characterize everything else as "DOS-like". 

As for the original challenge, I think you can actually get by with
overloading "[<-", leading to syntax of the form

LIST[a,b,c] <- f()

(which you most certainly would not want to inflict on standard R!)

LIST would want to be an object of class "foo" and
"[<-.foo" a
function that returns its first argument unchanged, and has its way
with the other arguments.

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at
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