R help - Oct 2004 - Ref: Variable scope or function behaviour or array reassign

Dear R- helpers

Following a draft structure of the R script for which I am facing problem

Step 1
x <-   of type array with original values
y <-   of type array  with original values


Step 2

for (ctr in 1:10) {

# my problem here the both x and y still show the original values from step 1
# in spite of making changes to the old values of the arrays x and y in the
function
   function (x,y)  ???

    }


step3


output < - function(parX,parY){

          Variables for New X and Y
	newx <- array(parX, dim=c(1,length(parX)))
	newy <- array(parY, dim=c(1,length(parY)))

                # make some calculation and updated some arrays element in the
newX and   # #newY


                       # finally assign the global  original values x and y with
newX and newY
                        
                       x<- newx
	           y<- newy
                      # if print here I can see the new values
                  
                       # but when the function gets called the second time  the
original values of
           #  x and y get called hence failing my motive of passing update
values of                  #the arrays to the function each time   ???
}
I believe there something to deal with env or new.env.... but never could get
the concept of the variable scope.....where the fact with the function the x and
y get updated but while calling from the main loop the x and y are pointing to
old values

  also I am keen to know as to is there a way to clear the array of old values
and reasign new values..or the <- operator take care of it by overwriting

regards
Kunal

Kunal Shetty wrote:
> Dear R- helpers
> 
> Following a draft structure of the R script for which I am facing problem
> 
> Step 1
> x <-   of type array with original values
> y <-   of type array  with original values
> 
> 
> Step 2
> 
> for (ctr in 1:10) {
> 
> # my problem here the both x and y still show the original values from step
1
> # in spite of making changes to the old values of the arrays x and y in the
function
>    function (x,y)  ???
> 
>     }
> 
> 
> step3
> 
> 
> output < - function(parX,parY){
> 
>           Variables for New X and Y
> 	newx <- array(parX, dim=c(1,length(parX)))
> 	newy <- array(parY, dim=c(1,length(parY)))
> 
>                 # make some calculation and updated some arrays element in
the newX and   # #newY
> 
> 
>                        # finally assign the global  original values x and y
with newX and newY
>                         
>                        x<- newx
> 	           y<- newy
>                       # if print here I can see the new values
>                   
>                        # but when the function gets called the second time 
the original values of
>            #  x and y get called hence failing my motive of passing update
values of                  #the arrays to the function each time   ???
> }
> I believe there something to deal with env or new.env.... but never could
get the concept of the variable scope.....where the fact with the function the x
and y get updated but while calling from the main loop the x and y are pointing
to old values
> 
>   also I am keen to know as to is there a way to clear the array of old
values and reasign new values..or the <- operator take care of it by
overwriting
> 
> regards
> Kunal
> 
> ______________________________________________
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I don't understand your question completely. Anyway, I guess you have 
missed the point that you can pass arguments to a function and that you 
can return an object (e.g. a list of other objects) from the function 
(please read "An Introduction to R" for more details).
Assign the value returned by a function it to an object in the calling 
function. In most circumstances, don't think too much about accessing 
environments, because you don't want to do it! The mechanisms mentioned 
above are sufficient in most circumstances.

Uwe Ligges