R help - Mar 2009 - add variable in for loop

Hi,

I'm learning to write some basic functions in R. For some data I have
I'd
like to be able to add a variable to itself after each iteration in a for
loop to obtain a grandtotal for that variable so I can calculate a mean.

test<-function(data){
	for (i in 1:80){

meanrotation<-(abs(data[i,3]-data[i,2])+abs(data[i,4]-data[i,2])+abs(data[i,5]-data[i,2])+abs(data[i,6]-data[i,2]))/4
	cat(i,meanrotation,"\n")
	#total+=meanrotation
	}
	#print (total/80)
	}

In perl there's an assignment operator variable+=variable2. Is there
anything like this in R to do as illustrated in the code above.

thanks a lot,

Paul

Edit - I guess the other way to do this which I just realised is to assign
the output of the function to a vector and then do a summary(), but I don't
know how to do this either - help is appreciated
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Hi Paul,

you do *not* want to do this, it takes too long and may lead to rounding 
errors. Vectorize everything, e.g., use sum(meanrotation). And look into 
?apply, and google for the "R Inferno".

And no, there is no "+="...

Good luck!
Stephan

pgseye schrieb:
> Hi,
> 
> I'm learning to write some basic functions in R. For some data I have
I'd
> like to be able to add a variable to itself after each iteration in a for
> loop to obtain a grandtotal for that variable so I can calculate a mean.
> 
> test<-function(data){
> 	for (i in 1:80){
> 
>
meanrotation<-(abs(data[i,3]-data[i,2])+abs(data[i,4]-data[i,2])+abs(data[i,5]-data[i,2])+abs(data[i,6]-data[i,2]))/4
> 	cat(i,meanrotation,"\n")
> 	#total+=meanrotation
> 	}
> 	#print (total/80)
> 	}
> 
> In perl there's an assignment operator variable+=variable2. Is there
> anything like this in R to do as illustrated in the code above.
> 
> thanks a lot,
> 
> Paul
> 
> Edit - I guess the other way to do this which I just realised is to assign
> the output of the function to a vector and then do a summary(), but I
don't
> know how to do this either - help is appreciated