[R] converting a for loop into a foreach loop

[kalee]

Dear all,

Just wondering if someone could help me out converting my code from a for()
loop into a foreach() loop or using one of the apply() function. I have a
very large dataset and so I'm hoping to make use of a parallel backend to
speed up the processing time. I'm having trouble getting selecting three
variables in the dataset to use in the foreach() loops. My for() loop code
is:

library(foreach)
library(multicore)
library(doMC)
registerDoMC()


> str(data)
'data.frame':	958 obs. of  13 variables:
 $ Date.Time: Factor w/ 260 levels "03/07/09 00:00",..: 1 2 2 2 3 3 3 3 3 3
...
 $ ID       : int  3 1 3 7 1 3 7 8 10 12 ...
 $ X        : num  151 151 151 151 151 ...
 $ Y        : num  -33.9 -33.9 -33.9 -33.9 -33.9 ...
 $ Z        : num  8 8 8 12 8 8 10 8 8 4 ...
 $ breeding : int  1 1 1 1 1 1 1 1 1 1 ...
 $ hour     : int  0 0 0 0 0 0 0 0 0 0 ...
 $ sex      : Factor w/ 4 levels "","F","M","U": 3 4 3 4 4 3 4 3 2 4 ...
 $ sex.code : int  1 3 1 3 3 1 3 1 2 3 ...
 $ day      : int  39997 39997 39997 39997 39997 39997 39997 39997 39997
39997 ...
 $ hour1    : int  24 24 24 24 24 24 24 24 24 24 ...
 $ X1       : num  1765688 1765492 1765492 1765637 1765383 ...
 $ Y1       : num  -3834667 -3834964 -3834964 -3834786 -3834990 ...


for (i in 1:15) {

x = data[data$ID == i, 1:10]

  for (j in 1:length(x$day)) {

  y = x[x$day == j, 1:10]

     for (k in 1:length(y$hour1)) {

    z = y[y$hour1 == k, 1:10]

   
H.scv <- Hscv(z, pilot = "unconstr")

KDE <- kde(z, H=H.scv, approx.cont=TRUE)
str(KDE)
head(KDE)

write.csv(KDE, file = paste("KDE",i j k,".csv"), row.names=T)

}
}
}

The foreach code I've tried (unsuccessfully) is:

x <- foreach(a = data[, 'ID'], .combine = "rbind") %:% foreach(b = data[ ,
'day'], .combine = "cbind") %:% foreach[c = data['hour1'], .combine
="cbind"] %dopar% {
   
   
H.scv <- Hscv((a,b,c), pilot = "unconstr")

KDE <- kde((a,b,c), H=H.scv, approx.cont=TRUE)
str(KDE)
head(KDE)

write.csv(KDE, file = paste("KDE",i,".csv"), row.names=T)

}

Many thanks for any help. 



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