R help - Feb 2010 - Appending results via for loop

Hey all,

So I'm manually conducting a sliding window test, and I would like to tack
on results to some variable as the results are outputted. I'm using a for
loop, and I am currently using an array as my 'output collector'
variable, though I know I should be using a dataframe of some sort. My question
is how to properly initialize a dataframe, and then add results to it as I go
through my for loop. Do I need to assign the size of the dataframe beforehand,
or can it be dynamic? I've read the help files and the mailing lists, but I
think I am not wording my question properly to find the right answers, so
I'm opting for this instead : )

Here's my code:

window <- 50
size <- 0
if (length(counts2$Count)<length(counts1$Count)) { size
<-length(counts2$Count) } else { size <- length(counts1$Count) }
a <- 0
b <- 0
alpha <- .05
n <- window
pval <- qchisq((1-(alpha / n)), 1)
results <- c(seq(1,size,window))
loop <- 1
for (i in seq(1,size,window)) {

	a <- i
	b <- i + window - 1
	countsavg <- (sum(abs(counts2$Count[a:b] - counts1$Count[a:b])))/length(a:b)
	countschisq <- ((abs(((counts2$Count[a:b] -
counts1$Count[a:b])-countsavg))^2)/countsavg)
	results[loop] <- countschisq
	loop <<- loop + 1

}

I'm guessing I'll be getting rid of the loop variable and the 'per
index' assignment thing, but I'm not sure what to do. Also, I'd like
to actually be grabbing 3 different groups of value per window, rather than just
one. So ultimately I'd like to have 3 columns in my data frame, and add to
each column every time I go through the data frame.

Thanks for your help everyone, really appreciate it,
~Michael

use a list:

result <- list()

for (i in 1:limit){
    ....computation....
    # store results
    result[[i]] <- yourData
}

On Fri, Feb 5, 2010 at 11:14 AM, Turchin, Michael
<Michael.Turchin at childrens.harvard.edu> wrote:
> Hey all,
>
> So I'm manually conducting a sliding window test, and I would like to
tack on results to some variable as the results are outputted. I'm using a
for loop, and I am currently using an array as my 'output collector'
variable, though I know I should be using a dataframe of some sort. My question
is how to properly initialize a dataframe, and then add results to it as I go
through my for loop. Do I need to assign the size of the dataframe beforehand,
or can it be dynamic? I've read the help files and the mailing lists, but I
think I am not wording my question properly to find the right answers, so
I'm opting for this instead : )
>
> Here's my code:
>
> window <- 50
> size <- 0
> if (length(counts2$Count)<length(counts1$Count)) { size
<-length(counts2$Count) } else { size <- length(counts1$Count) }
> a <- 0
> b <- 0
> alpha <- .05
> n <- window
> pval <- qchisq((1-(alpha / n)), 1)
> results <- c(seq(1,size,window))
> loop <- 1
> for (i in seq(1,size,window)) {
>
> ? ? ? ?a <- i
> ? ? ? ?b <- i + window - 1
> ? ? ? ?countsavg <- (sum(abs(counts2$Count[a:b] -
counts1$Count[a:b])))/length(a:b)
> ? ? ? ?countschisq <- ((abs(((counts2$Count[a:b] -
counts1$Count[a:b])-countsavg))^2)/countsavg)
> ? ? ? ?results[loop] <- countschisq
> ? ? ? ?loop <<- loop + 1
>
> }
>
> I'm guessing I'll be getting rid of the loop variable and the
'per index' assignment thing, but I'm not sure what to do. Also,
I'd like to actually be grabbing 3 different groups of value per window,
rather than just one. So ultimately I'd like to have 3 columns in my data
frame, and add to each column every time I go through the data frame.
>
> Thanks for your help everyone, really appreciate it,
> ~Michael
> ______________________________________________
> 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.
>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?