Hi:
I *think* this is what you're after, but I get dizzy trying to read
convoluted loops. Try this instead;
# Function to find the total SBA2 for all dbh2 larger than the given one:
foo <- function(d) {
d <- d[order(d$dbh2), ]
d <- transform(d, BAL2 = sum(SBA2) - cumsum(SBA2))
d
}
library('plyr')
ddply(kk, .(Plot), foo)
Pma Plot dbh2 SBA2 BAL2
1 29 1 185.8568 9.055821 91.530165
2 33 1 186.4623 10.762347 80.767818
3 1 1 192.8324 10.741988 70.025830
4 17 1 196.2093 9.484601 60.541229
5 21 1 204.0971 11.389817 49.151412
6 13 1 204.5070 9.644655 39.506756
7 9 1 205.3079 11.014892 28.491864
8 25 1 206.5908 10.041878 18.449986
9 5 1 206.8110 8.602678 9.847307
10 37 1 211.1735 9.847307 0.000000
...
# If you want the groupwise sum in the output, use the following
version instead:
foo <- function(d) {
d <- d[order(d$dbh2), ]
d <- transform(d, BAL2 = sum(SBA2) - cumsum(SBA2),
aa = sum(SBA2))
d
}
HTH,
Dennis
On Thu, Jul 21, 2011 at 4:13 AM, paloma ruiz benito
<paloma_...@hotmail.com> wrote:
>
> Hi everyone,
>
> I have been working some days in a nested loop in R but I can't find the
> solution.
>
> I have a data.frame with an unique ID for individuals and unique ID for
> different stands, for each indiviadual I have a dbh record and a SBA (stand
> basal area) field.
>
> Pma<-rep (1:40)
> P<-seq(1,4, 1)
> Plot<-rep(P,10)
> dbh2<-rnorm(40, mean=200, sd=5)
> SBA2<-rnorm(40, mean=10, sd=1)
>
> As I want to calculate the basal area of larger trees in each stand (i.e.,
> the compare tree to tree the dbh and for each individual sum the stand basal
> area of larger trees)
>
> BAL2<-rep(0,length(Pma))
> aa<-rep(0,length(Pma))
>
> Now I have programed a for loop to do this calculation, and one plot it works
> quite well:
>
> kk<-data.frame(Pma, Plot, dbh2, SBA2, BAL2, aa)
> kkk<-kk[kk$Plot=="1",]
>
>
> The loop:
>
> for(j in 1:length(kkk$Pma)){
> for(i in 1:length(kkk$Pma)){
> if(kkk$dbh2[j]<kkk$dbh2[i])
> kkk$aa[i]<-kkk$SBA2[i]
> else temp_data$aa[i]<-0
> kkk$BAL2[j]<-sum(kkk$aa)
> }
> }
>
> But, I have tried a million of forms to calculate this for each stand... and
> no one looks fine. The closest code that I have got is:
>
> for(k in 1:length(kk)){
> temp_data<-kk[kk$Plot==Plot[k],]
>
> for(j in 1:length(temp_data$Pma)){
> #I have selected the individuals to calculate the BAL in each plot
> for(i in 1:length(temp_data$Pma)){
> if(temp_data$dbh2[j]<temp_data$dbh2[i])
> temp_data$aa[i]<-temp_data$SBA2[i]
> else temp_data$aa[i]<-0
> temp_data$BAL2[j]<-sum(temp_data$aa)
>
>
> }
>
> ###Some suggestion to "save" the temporal data of each stand and group it
> together
> }
>
> }
>
> Any advise or suggestion will be very welcome,
>
> Thanks in advance,
>
> Paloma
>
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@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@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.
