Monica, You can try the following:
> x.tot <- aggregate(x$val, by=list(total=x$locat), 'sum') > x.tot total x 1 a 5 2 b 20 3 c 40 4 d 30 > cbind(x, perc=x$val/rep(x.tot$x, table(x$locat)) * 100) locat val perc 1 a 5 100.00000 2 b 5 25.00000 3 b 15 75.00000 4 c 5 12.50000 5 c 20 50.00000 6 c 5 12.50000 7 c 10 25.00000 8 d 5 16.66667 9 d 15 50.00000 10 d 10 33.33333 -Christos > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Monica Pisica > Sent: Thursday, March 13, 2008 9:36 AM > To: r-help@r-project.org > Subject: [R] a more elegant way to get percentages? > > > Hi, > > I am trying to get percentages in a more elegant way. I have > a data.frame with locations and values (counts) of species at > that location. Each location is repeated for each species i > have values for and i would like to get percentages of each > species at that location. I am not sure if i am clear in my > explanations so i will paste my code below: > > ##################### > > > x > locat val > 1 a 5 > 2 b 5 > 3 b 15 > 4 c 5 > 5 c 20 > 6 c 5 > 7 c 10 > 8 d 5 > 9 d 15 > 10 d 10 > > loc1 <- x$locat > > n <- length(loc1) > > locuniq1 <- unique(loc1) > > m <- length(locuniq1) > > counts <- seq(1:m) > > > > for (i in 1:m) { > + count <- 0 > + for (j in 1:n) { > + if (loc1[j]==locuniq1[i]) count <- count+1 counts[i] <- count } } > > > > percent1 <- rep(0,n) > > j <- 0 > > for (i in 1:m) { > + > + b <- x[(j+1):(j+counts[i]),] > + total <- sum(b$val) > + percent1[(j+1):(j+counts[i])] <- round(apply(as.matrix(b$val), 1, > + function(x) {x*100/total}),2) j = j+counts[i] } > > x1 <- cbind(x, percent1) # this is the result i want > > x1 > locat val percent1 > 1 a 5 100.00 > 2 b 5 25.00 > 3 b 15 75.00 > 4 c 5 12.50 > 5 c 20 50.00 > 6 c 5 12.50 > 7 c 10 25.00 > 8 d 5 16.67 > 9 d 15 50.00 > 10 d 10 33.33 > > > ################ > > I am wondering if there is any way to do it more efficiently, > much more that the first loop which gives how many times each > location is present in the data.frame is slow if you have a > larger data.frame and not only 10 rows. > > Thanks for any input and sorry if the email is on the long side, > > Monica > > > _________________________________________________________________ > [[elided Hotmail spam]] > > ______________________________________________ > 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.
