[R] Build a dataframe row by row?

[Gavin Simpson]

On Wed, 2009-08-05 at 10:28 +1000, Remko Duursma wrote:
> > Nice, but I need a few columns for the data.  Don't know how to do this with
> > the method you suggest.
> 
> For each iteration, you make a vector of your 'data', in the example
> it is a vector of length 3.
> Each of the elements in this vector will become a column in the dataframe.
> 
> If that is not what you mean, can you give a specific example?
> 
> remko

If you know that there will be 10 rows then why not allocate the DF
initially and fill in by row during the loop?

nc <- 3
nr <- 10
df <- data.frame(matrix(NA, ncol = nc, nrow = nr))
for(i in seq_len(nr)) {
	## Noah can fill in the "cells" as he goes with various results
	## the below is just to illustrate
	df[i,1] <- rnorm(1)
	df[i,2] <- runif(1)
	df[i,3] <- rpois(1, 4)
}
df

G

> 
> 
> 
> > -N
> >
> > On 8/4/09 4:57 PM, Remko Duursma wrote:
> >>
> >> Hi Noah,
> >>
> >> there are a few ways to do this. Easiest is to keep adding an element
> >> to a list, and then make it into a dataframe at the end, like this:
> >>
> >> resultlis<- list()
> >> for(i in 1:10){
> >>
> >> # your calculations here
> >> datavec<- runif(3)
> >>
> >> resultlis[[i]]<- datavec
> >>
> >> }
> >> resultdfr<- as.data.frame(do.call("rbind", resultlis))
> >>
> >>
> >> greetings,
> >> Remko
> >>
> >> -------------------------------------------------
> >> Remko Duursma
> >> Post-Doctoral Fellow
> >>
> >> Centre for Plants and the Environment
> >> University of Western Sydney
> >> Hawkesbury Campus
> >> Richmond NSW 2753
> >>
> >> Dept of Biological Science
> >> Macquarie University
> >> North Ryde NSW 2109
> >> Australia
> >>
> >> Mobile: +61 (0)422 096908
> >> www.remkoduursma.com
> >>
> >>
> >>
> >> On Wed, Aug 5, 2009 at 9:41 AM, Noah Silverman<noah at smartmediacorp.com>
> >>  wrote:
> >>
> >>>
> >>> Hi,
> >>>
> >>> Time for another of my "newbie" questions.
> >>>
> >>> Is it possible to build up a data.frame "row by row" as I go
> >>>
> >>> I'm going to be running a bunch of experiments (many in a loop) to test
> >>> different things.  I'm using AUC as my main performance measure.
> >>>
> >>> My thought was to add a row to a data.frame for each iteration and then
> >>> have
> >>> a nice summary report at the end.
> >>>
> >>> I found how to import, export, and create from vectors.  I haven't been
> >>> able
> >>> to find how just make an empty one and add rows as I go.
> >>>
> >>> ______________________________________________
> >>> R-help at 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 at 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.
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