I like the Venables and Ripley reasoning around the assignment
character: use different characters for assignment in different
environments. So you have = for assignment inside function calls, <- for
assignment in the current environment, and <<- for assignment in the
global environment.
Cheers,
Simon.
On 27/10/10 10:41, Murray Jorgensen wrote:
I can see that I am going to have to set a little context because I
wanted to anchor the discussion in the teaching of statistics, and not
of R as a language. I think the issues are different in the two. One
big problem in the former is that symbols can engender fear in the
students.
A few years ago I was taken off the teaching of a large first year
business statistics course. The clinching incident in this decision
mentioned by my then chairperson was the use ( in a side-discussion )
of the mathematical summation sign ( upper-case Greek sigma ). I
don't think my chairperson was wrong. In the context of that course
what I should have done was illustrate my point with a column of data
in an Excel spreadsheet.
If \Sigma upsets business students with its suggestion of abstract
mathematics, I think many other statistics students find <- somewhat
suggestive of abstract logic or theoretical computer science,
favourite subjects of an epsilonic proportion of the large classes I
used to teach.
I teach smaller classes now and my students come to me with previous
exposure to Minitab which uses = for assignment. I use = both to avoid
any of the symbol-fear that I spoke of, and also because they are used
to how assignment works in Minitab. (For maybe half of the students,
Minitab would be the only computer language that they would have met.)
I will come clean and admit that I have another reason for not liking R.
The symbol <- suggests the right-to-left direction of the assignment
strongly and appropriately. But I read from left-to-right and I get
startled by an arrow coming at me from the unseen future and feel a
second or two of cognitive dissonance.
I actually rather like the right-pointing -> assignment as the
directions of reading and of computation agree. It would be a bit
idiosyncratic to use it in code though. I find it useful in
interactive R when I have typed and evaluated a complex expression and
realise that I really should have assigned it to something. After the
up-arrow key -> lets me do the needed assignment on the right of the
expression.
Murray
On 27/10/2010 12:59 p.m., Gabor Grothendieck wrote:
On Tue, Oct 26, 2010 at 3:10 PM, Murray Jorgensen<[email protected]>
wrote:
Greetings all,
in my own R code I have used various forms of the R assignment
operator at
different times in my life. There are arguments for and against each
choice.
A question I would like this sig is whether there are any specifically
teaching reasons for preferring one form over another?
A second question, mainly to clarify the first, is whether different
forms
might be preferred for different types of student?
Awaiting responses with interest - Murray
<- is less error prone so you always want to use that. It might be
argued that there are only a few cases where it matters but if you run
into one of those cases you will be sorry you did not standardize on
using<- .
--
Simon Blomberg, BSc (Hons), PhD, MAppStat, AStat
Lecturer and Consultant Statistician
School of Biological Sciences
The University of Queensland
St. Lucia Queensland 4072
Australia
T: +61 7 3365 2506
email: S.Blomberg1_at_uq.edu.au
http://www.uq.edu.au/~uqsblomb/
Policies:
1. I will NOT analyse your data for you.
2. Your deadline is your problem
Statistics is the grammar of science - Karl Pearson.
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