[R] Incrementally building histograms

[Gabor Grothendieck]

You can eliminate the loop like this (untested):

cnt <- function(file) {
 data <- scan(file, quiet = TRUE)
 hist(data, plot = FALSE, breaks = breaks)$counts
}
Reduce("+", sapply(files, cnt))


On Wed, Nov 5, 2008 at 8:01 PM, Andre Nathan <andre at digirati.com.br> wrote:
> Hello
>
> I need to build a histogram from data (numbers in the [0,1] interval)
> stored in a number of different files. The total amount of data is very
> large, so I can't load everything to memory and then simply call hist().
> Since what I actually need are the histogram counts, I'm currently doing
> it like this:
>
> breaks <- seq(0, 1, by = 0.01)
> files <- list.files(pattern = "some pattern")
> counts <- 0
> for (file in files) {
>  data <- scan(file, quiet = T)
>  h <- hist(data, plot = F, breaks = breaks)
>  counts <- counts + h$counts
> }
> # and then work with `counts' here
>
> Is there a more efficient and/or idiomatic way to do this?
>
> Thanks,
> Andre
>
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