[R] Check for is.object
Hello, I am trying to recursively append some data from multiple files into a common object For this, I am using in a loop NewObject - rbind(NewObject,tempObject) For the first loop, obviously there is no NewObject ... so I wanted to do NewObject - tempObject[0,] Now when it loops again I want to put the statement do NewObject - tempObject[0,] inside a if statement ... so that it does I can skip it once NewObject has been initialized. But, is.object doesn't seem to work. What is the alternative check that I can do? And is there a better way to achieve what I want? Thanks, S __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] Check for is.object
I think you want the function ?exists if(!exists(NewObject)) -- 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-boun...@r-project.org wrote on 11/22/2010 10:14:51 AM: [image removed] [R] Check for is.object Santosh Srinivas to: r-help 11/22/2010 10:17 AM Sent by: r-help-boun...@r-project.org Hello, I am trying to recursively append some data from multiple files into a common object For this, I am using in a loop NewObject - rbind(NewObject,tempObject) For the first loop, obviously there is no NewObject ... so I wanted to do NewObject - tempObject[0,] Now when it loops again I want to put the statement do NewObject - tempObject[0,] inside a if statement ... so that it does I can skip it once NewObject has been initialized. But, is.object doesn't seem to work. What is the alternative check that I can do? And is there a better way to achieve what I want? Thanks, S __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] Check for is.object
Santosh -
The simple answer to your question is to initialize
NewObject to NULL before the loop, i.e.
newObject = NULL
However, I should point out this is one of the most
inefficient ways to program in R. A far better way is
to allocate enough space for NewObject outside your
loop, and fill it in in the loop. Here's a simple
example to give you an idea of the difference in time
the two methods require:
system.time({answer = matrix(NA,1000,5);
+ for(i in 1:1000)answer[i,] - sample(10,5)})
user system elapsed
0.020 0.000 0.017
system.time({answer=NULL;
+ for(i in 1:1000)answer=rbind(answer,sample(10,5))})
user system elapsed
0.072 0.000 0.070
However, it gets even worse if the sample size is larger:
system.time({answer = matrix(NA,1,5);
+ for(i in 1:1)answer[i,] - sample(10,5)})
user system elapsed
0.184 0.000 0.184
system.time({answer=NULL;for(i in 1:1)
+ answer=rbind(answer,sample(10,5))})
user system elapsed
5.492 0.032 5.562
Even if you don't know how big your newObject matrix will
become, it's still far more efficient to overallocate the
matrix and then truncate it at the end.
I'd strongly recommend that you avoid building your matrix
incrementally inside a loop!
- Phil Spector
Statistical Computing Facility
Department of Statistics
UC Berkeley
spec...@stat.berkeley.edu
On Mon, 22 Nov 2010, Santosh Srinivas wrote:
Hello,
I am trying to recursively append some data from multiple files into a
common object
For this, I am using in a loop
NewObject - rbind(NewObject,tempObject)
For the first loop, obviously there is no NewObject ... so I wanted to do
NewObject - tempObject[0,]
Now when it loops again I want to put the statement do NewObject -
tempObject[0,] inside a if statement ... so that it does I can skip it once
NewObject has been initialized.
But, is.object doesn't seem to work.
What is the alternative check that I can do? And is there a better way to
achieve what I want?
Thanks,
S
__
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
__
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
