R help - Mar 2011 - indeterminate for loop

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

?"while"
You don't want a for loop. You need a while loop.
--------------------------------------
Jonathan P. Daily
Technician - USGS Leetown Science Center
11649 Leetown Road
Kearneysville WV, 25430
(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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