[R] Simple Function

[David Winsemius]

On Nov 10, 2010, at 3:47 AM, Nick Sabbe wrote:

> Hi Nikos.
>
> There is quite a bit going on here, both in the code and in your
> terminology.
> You should really consider reading "An introduction to R" that comes  
> with
> your R installation.
>
> A few pointers though:
> * in R speak, you have nowhere "declared 2 global matrices": it is not
> completely clear why you use code like "y<-c(NA)" to try to achieve  
> such a
> thing, but if I'm not mistaken, this creates a logical vector of  
> length 1.
> Surely not a matrix.
> * operator <- only looks for variables in the environment in which  
> they are
> evaluated,

Not really true. Looks first in the local environment but if not  
present, looks successively in the enclosing environments.

> as does = (note: I would advise you to use <- in R as an
> assignment operator instead of =). If you want to change variables  
> in other
> environments, particularly the global environment, you need to use  
> <<- (?<<-
> does not seem to work to get you to its help page,

Use:
 > ?"<<-"


> but open R help, then
> find the search page and search for <<-, for more information).
> * apart from that: you may want to avoid the for loop here altogether:
> y[i:10]<-(i:10)+1
> f[i:10]<-y[(i-1):9]/2
> gives you the same result, but more in the R fashion (in general,  
> you want
> to avoid explicit for loops in R)
>
> HTH,
>
>
> Nick Sabbe
> --
> ping: nick.sabbe at ugent.be
> link: http://biomath.ugent.be
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> ring: 09/264.59.36
>
> -- Do Not Disapprove
>
>
>
>
> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org 
> ] On
> Behalf Of rnick
> Sent: woensdag 10 november 2010 7:51
> To: r-help at r-project.org
> Subject: [R] Simple Function
>
>
> Hi guys,
>
> Very new to R and your help would be highly appreciated for the  
> following
> problem. I am trying to create a simple function which registers  
> values
> within an array through a for loop. These are the steps I have  
> followed:
>
> 1) Declared 2 global matrices
> 2) Create function mat() with i as an input
> 3) constructed the for loop
> 4) called mat(2)
>
> The problem is that when i try to get y[4] and f[5] the output is:  
> [1] NA
>
> my concern is that i am not addressing any of the following topics:
> 1) definition of global variable
> 2) the argument does not go through the for loop
> 3) the matrices definition is not correct
> 4) other
>
> Please check my code below:
>
> y=c(NA)
> f=c(NA)
> mat<-function(i)
> {
> 	for (k in i:10)
> 	{
> 		y[k]=k+1
> 		f[k]=y[k-1]/2		
> 	}
> }
> mat(2)
>
> Any thoughts or recommendations would be highly appreciated.
>
> Thanks in advance,
>
> N
> -- 
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