"On average, any data manipulation that can be described in a sentence or two of English can be programmed in one line in R. If you find yourself writing a long 'for' loop to do something that sounds simple, take a step back and research if an existing combination of functions can easily handle your request."
-- Erik Iverson I nominate this for a Fortune. (email thread in which it appeared below) -- Bert Bert Gunter Genentech Nonclinical Biostatistics -----Original Message----- From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On Behalf Of Erik Iverson Sent: Thursday, June 24, 2010 4:14 PM To: john polo Cc: r-help@r-project.org Subject: Re: [R] write a loop for tallies On average, any data manipulation that can be described in a sentence or two of English can be programmed in one line in R. If you find yourself writing a long 'for' loop to do something that sounds simple, take a step back and research if an existing combination of functions can easily handle your request. john polo wrote: > Dear R users, > > I have a list of numbers such as > > > n > [1] 3000 4000 5000 3000 5000 6000 4000 5000 7000 5000 6000 7000 > > and i'd like to set up a loop that will keep track of the number of > occurences of each of the values that occur in the list, e.g. > > 3000: 2 > 4000: 2 > 5000: 4 > > I came up with the following: > > a<- for (i in 1:length(n)) { > r<-0 > s<-0 > t<-0 > u<-0 > v<-0 > ifelse(n[i] == "3000", r <- r+1, > ifelse(n[i] == "4000", s <- r+1, > ifelse(n[i] == "5000", t <- r+1, > ifelse(n[i] == "6000", u <- r+1, > ifelse(n[i] == "7000", v <- r+1, NA))))) > r<-sum(r) > s<-sum(s) > t<-sum(t) > u<-sum(u) > v<-sum(v) > cat("r = ", r, "\n") > cat("s = ", s, "\n") > cat("t = ", t, "\n") > cat("u = ", u, "\n") > cat("v = ", v, "\n") > } > > However, this is the output: > > r = 1 > s = 0 > t = 0 > u = 0 > v = 0 > r = 0 > s = 1 > t = 0 > u = 0 > v = 0 > r = 0 > s = 0 > t = 1 > u = 0 > v = 0 > r = 1 > s = 0 > t = 0 > u = 0 > v = 0 > r = 0 > s = 0 > t = 1 > u = 0 > v = 0 > r = 0 > s = 0 > t = 0 > u = 1 > v = 0 > r = 0 > s = 1 > t = 0 > u = 0 > v = 0 > r = 0 > s = 0 > t = 1 > u = 0 > v = 0 > r = 0 > s = 0 > t = 0 > u = 0 > v = 1 > r = 0 > s = 0 > t = 1 > u = 0 > v = 0 > r = 0 > s = 0 > t = 0 > u = 1 > v = 0 > r = 0 > s = 0 > t = 0 > u = 0 > v = 1 > > How should i write this loop, please? I've tried variations with "if" > instead of "ifelse" and receive errors about "unexpected {" or > "unexpected )". > > regards, > john > > ______________________________________________ > 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. ______________________________________________ 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.
