R help - May 2009 - Simulation)

I wrote

 As a beginner, I agree .... the for loop is much clearer to me.  

Wacek Kusnierczyk <Waclaw.Marcin.Kusnierczyk at idi.ntnu.no> replied
>
>well, that's quite likely.  especially given that typical courses in
>programming, afaik, include for looping but not necessarily functional
>stuff -- are you an r beginner, or a programming beginner? 
>
Both.  My PhD is in psychometrics, and, both in course work and since then
I've learned a good bit of statistics, but very little programming. 
I've
picked up a little SAS programming over the years, but not much.  

But the loop (at least for me) translates into English more directly than the
lapply statement does.

>among the perl packages i have ever downloaded from cran, it's hard to
>find one without a for loop, but it's easy to find one without a map. 
>but it's not necessarily because for loops are easier;  just that
that's
>the way people are typically taught to program. 
>
>the structure and interpretation of computer programs (sicp) by abelson
>& sussman, a beautiful cs masterpiece, introduces mapping (lapplying) on
>p. 105, mentions a for-each control abstraction only in an exercise two
>pages later, and does not really discuss for looping as such. 
>functional mapping over stateless objects is, in general, *much* easier
>to reason with than procedural looping over stateful objects -- an issue
>a beginner may not be quite aware of, and learning the basic for loop
>stuff without caring about, e.g., concurrent access to shared mutable
>state etc. may indeed make the impression that for  loops are easier. 
>
>anyway, once you've learned for loops, it's not a bad idea to learn
>lapply.  and once you've learned lapply, you'll probably not go back
to
>for loops that easily.
>
Would that be a good book for a beginner?

Peter

Peter L. Flom, PhD
Statistical Consultant
www DOT peterflomconsulting DOT com

Peter Flom wrote:
>  As a beginner, I agree .... the for loop is much clearer to me.  
>
>   
>> well, that's quite likely.  especially given that typical courses
in
>> programming, afaik, include for looping but not necessarily functional
>> stuff -- are you an r beginner, or a programming beginner? 
>>
>>     
>
> Both.  My PhD is in psychometrics, and, both in course work and since then
> I've learned a good bit of statistics, but very little programming. 
I've
> picked up a little SAS programming over the years, but not much.
>   
don't really know sas, but i guess for looping is of essence there,
while mapping is not.
> But the loop (at least for me) translates into English more directly than
the
> lapply statement does.
>   
lapply easily translates to 'apply this to every item there', which is
roughly an alternative version of 'for each item in there, do this with
the item'.

>>
>> the structure and interpretation of computer programs (sicp) by abelson
>> & sussman, a beautiful cs masterpiece, introduces mapping
(lapplying) on
>> p. 105, mentions a for-each control abstraction only in an exercise two
>> pages later, and does not really discuss for looping as such. 
>> functional mapping over stateless objects is, in general, *much* easier
>> to reason with than procedural looping over stateful objects -- an
issue
>> a beginner may not be quite aware of, and learning the basic for loop
>> stuff without caring about, e.g., concurrent access to shared mutable
>> state etc. may indeed make the impression that for  loops are easier. 
>>
>>     
> Would that be a good book for a beginner?
>   

both yes and no.  this is a book that can be used by an absolute
beginner in programming, but if you're focused on statistics, you're
unlikely to enjoy it, at least not as a practical introduction.  but
it's a good read, and contains quite a lot of useful ideas anyway.

vQ