Hello everybody,
I have written a nested for-loop, but as length(uc) > 170,000, this would
take VERY long. I have tried to use sapply or something but I cannot get it
to work, I would be happy if someone could point out to write this more
efficiently. Thank you all,
Ludwig
ergsens <- data.frame(budget = numeric(500))
uc <- unique(rftab$startCell)
for(i in 1:500){
uniquerates <- rlnorm(n = length(uc), mean = -1.6, sd = 1.7)
for(j in 1:length(uc)){
rftab$masskg[rftab$startCell == uc[j]] <- uniquerates[j]
}
ergsens$budget[i] <- sum(rftab$masskg, na.rm = TRUE)/1000
}
-----
Dipl. Geogr. Ludwig Hilger
Wiss. MA
Lehrstuhl f?r Physische Geographie
Katholische Universit?t Eichst?tt-Ingolstadt
Ostenstra?e 18
85072 Eichst?tt
--
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I cannot run your code because not all the variables are defined, but
try not doing the nested replacements, rftab$masskg[...] <- newValue,
in the loop. Instead, pull out masskg as a new stand-along object
before the start of the loop and put it back into rftab at the end of
the loop. E.g., something like
masskg <- rftab$masskg
for(i in 1:500){
uniquerates <- rlnorm(n = length(uc), mean = -1.6, sd = 1.7)
for(j in 1:length(uc)){
masskg[rftab$startCell == uc[j]] <- uniquerates[j]
}
ergsens$budget[i] <- sum(masskg, na.rm = TRUE)/1000
}
rftab$masskg <- masskg
# and you may as well remove masskg now.
If that doesn't help enough, look into the ave() function or the
functions in plyr.
Bill Dunlap
TIBCO Software
wdunlap tibco.com
On Thu, May 8, 2014 at 12:59 PM, Ludwig Hilger <l.hilger at ku.de>
wrote:> Hello everybody,
> I have written a nested for-loop, but as length(uc) > 170,000, this
would
> take VERY long. I have tried to use sapply or something but I cannot get it
> to work, I would be happy if someone could point out to write this more
> efficiently. Thank you all,
>
> Ludwig
>
> ergsens <- data.frame(budget = numeric(500))
> uc <- unique(rftab$startCell)
>
> for(i in 1:500){
> uniquerates <- rlnorm(n = length(uc), mean = -1.6, sd = 1.7)
> for(j in 1:length(uc)){
> rftab$masskg[rftab$startCell == uc[j]] <- uniquerates[j]
> }
> ergsens$budget[i] <- sum(rftab$masskg, na.rm = TRUE)/1000
> }
>
>
>
>
>
> -----
> Dipl. Geogr. Ludwig Hilger
> Wiss. MA
> Lehrstuhl f?r Physische Geographie
> Katholische Universit?t Eichst?tt-Ingolstadt
> Ostenstra?e 18
> 85072 Eichst?tt
> --
> View this message in context:
http://r.789695.n4.nabble.com/How-can-I-make-this-nested-loop-faster-tp4690209.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
Your code is not re-producable. Can you provide a working example using a standard dataset from R? But, you could first try to use compiler package, see ?enableJIT. Another option would be to use doMC/foreach packages if you can run your assignment in the nested loop in parallel, see %dopar%. On 8 May 2014 21:59, Ludwig Hilger <l.hilger at ku.de> wrote:> Hello everybody, > I have written a nested for-loop, but as length(uc) > 170,000, this would > take VERY long. I have tried to use sapply or something but I cannot get it > to work, I would be happy if someone could point out to write this more > efficiently. Thank you all, > > Ludwig > > ergsens <- data.frame(budget = numeric(500)) > uc <- unique(rftab$startCell) > > for(i in 1:500){ > uniquerates <- rlnorm(n = length(uc), mean = -1.6, sd = 1.7) > for(j in 1:length(uc)){ > rftab$masskg[rftab$startCell == uc[j]] <- uniquerates[j] > } > ergsens$budget[i] <- sum(rftab$masskg, na.rm = TRUE)/1000 > } > > > > > > ----- > Dipl. Geogr. Ludwig Hilger > Wiss. MA > Lehrstuhl f?r Physische Geographie > Katholische Universit?t Eichst?tt-Ingolstadt > Ostenstra?e 18 > 85072 Eichst?tt > -- > View this message in context: http://r.789695.n4.nabble.com/How-can-I-make-this-nested-loop-faster-tp4690209.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > 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.