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for loops?

5 messages · Catherine Stein, Pedro Rodrigues, Barry Rowlingson +2 more

Catherine Stein
# 
Hello R people!

How can one use a for loop (or something similar) in R?  As I type in each
line, I get syntax errors... I'm just confused how much to type in at each
">" prompt.

Thanks for your help,
cathy



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Catherine M. Stein
Research Assistant, Tuberculosis Research Unit
Doctoral Candidate in Genetic Epidemiology
Department of Epidemiology and Biostatistics
Case Western Reserve University
office: (216)368-0875 or (216)778-1378
e-mail: kasia at darwin.cwru.edu, or cmstein at cwru.edu
http://darwin.cwru.edu/~kasia

EPBI Student Resources Page:
http://hal.epbi.cwru.edu/stures/
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Pedro Rodrigues
#
On Mon, 2004-02-02 at 13:42, Catherine Stein wrote:
Hello.

I believe you want something like:

for(i in 1:n){
...some lines here...
}

If you have only one line within the for loop you can use it without the
brackets.

If the environment is still open (as within the for loop) you will not
get a new ">" prompt but a "+" prompt to continue as if you were writing
on the same line.

Only when you close the brackets the prompt will return to ">" after
executing the for loop.

Hope this will help.

Pedro
Barry Rowlingson
#
Catherine Stein wrote:

            

      
      
      
    

        
Have you read help("for") (you need to quote 'for' here to avoid a 
syntax error!)?

  If you'd shown us exactly what you'd typed we could probably help 
better. Suppose you want to loop from 1 to 10 and print it. You can do 
the following, where '>' is the R prompt (dont type it):

  > for(i in 1:10)print(i)
     - ie all on one line

  > for(i in 1:10){print(i)}
     - with curly brackets

  > for(i in 1:10)
  + print(i)

    - where '+' is the continuation prompt (dont type it) - R gives you 
this when it realises you havent written a complete expression yet.

  > for(i in 1:10) {
  + print(i)
  + }

     - curly brackets enclose as many expressions as you like inside the 
loop.

  > for(i in 1:10)
  + { print(i)
  + }

     - curly brackets anywhere. R works it out.

  You can even do, and I didn't think this would work...

  > for(i in
  + 1:10)
  + {print(i)}


  So in short, I cant get it to give a syntax error :) What are you 
doing? What version of R, and what platform?

Baz

  
  


  


      

    

    

      
      

        


  

        

      PIKAL Petr
    

    

      
      #
    

  


  

      
Hi

        
On 2 Feb 2004 at 8:42, Catherine Stein wrote:

        

            

      
      
      
    

        
Use curly braces
for (i in ...) {

your long commands
in several lines

}

"An Introduction to R" in doc directory is your best friend.

Cheers
Petr

            

      
      
      
    

        

      
      
    

        
Petr Pikal
petr.pikal at precheza.cz

  
  


  


      

    

    

      
      

        


  

        

      Winfried Theis
    

    

      
      #
    

  


  

      
Hello Cathy

you should open some curly brackets after the "for" statement e.g.

for(i in 1:1000){
print("Hello!")
print(sum(15+i*3))
}

or simlarly. But please keep in mind that R is rather slow with loops.
So have a look at apply & friends and check if you can rephrase your
problem to use them.

cheers,

Winni

        
On Mon, 2004-02-02 at 14:42, Catherine Stein wrote: