[R] indeterminate for loop

[lm609 at york.ac.uk]

Thanks! I've never come across 'while' before and it's perfect.


On Mar 15 2011, Jonathan P Daily wrote:

>?"while"
>You don't want a for loop. You need a while loop.
>--------------------------------------
>Jonathan P. Daily
>Technician - USGS Leetown Science Center
>11649 Leetown Road
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>(304) 724-4480
>"Is the room still a room when its empty? Does the room,
> the thing itself have purpose? Or do we, what's the word... imbue it."
>     - Jubal Early, Firefly
>
>r-help-bounces at r-project.org wrote on 03/15/2011 10:14:21 AM:
>
>> [image removed] 
>> 
>> [R] indeterminate for loop
>> 
>> lm609 
>> 
>> to:
>> 
>> r-help
>> 
>> 03/15/2011 10:16 AM
>> 
>> Sent by:
>> 
>> r-help-bounces at r-project.org
>> 
>> Hello,
>> 
>> I have written a 'for' loop which on the first run makes nearest 
>neighbour 
>> calculations for my dataset 'A' in relation to dataset 'B', then based 
>on 
>> these results, some of the rows from A are moved into dataset B, and the 
>
>> calculation is repeated on the remaining rows in A. Therefore a smaller 
>and 
>> smaller amount of data is analysed as the loop proceeds, since A is 
>losing 
>> rows each time. The results of the calculation change as less data is 
>used, 
>> but not in a predictable way, therefore the end point of the loop is 
>> indeterminate.
>> 
>> The script is long and the datasets big, but a simplified example where 
>'A' 
>> and 'B' are datasets, and the function 'ndist2' calculates 'x' is...
>> 
>> for (i in 1:100)
>> {
>> C <- data.frame(ndist2(B,A))
>> C1 <- subset(C, x = min(C$x))
>> B <- rbind(B, C1)
>> A <- subset(C, x > min(C$x))
>> }
>> 
>> So eventually A runs out.
>> 
>> Currently, I let the loop run until a warning comes up which effectively 
>
>> says no more data, and at this point it is finished.
>> 
>> What I would now like to do is place this loop inside another loop in 
>order 
>> to run through multiple datasets, but I can't do this when the script 
>> produces a warning message at the end of each dataset.
>> 
>> Is there any way I can overcome this problem?
>> 
>> Thanks for your help,
>> Louise
>> 
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>