loop is too slow. it appears that sparseMatrix does what I want: ll <- lapply(l,length) i <- rep(1:4, ll) vv <- unlist(l) j1 <- as.factor(substring(vv,1,1)) t <- table(j1) j <- position of elements of j1 in names(t) sparseMatrix(i,j,x=as.numeric(substring(vv,2,2)), dimnames = names(t))
so, the question is, how do I produce a vector of positions? i.e., from vectors [1] "A" "B" "A" "C" "A" "B" and [1] "A" "B" "C" I need to produce a vector [1] 1 2 1 3 1 2 of positions of the elements of the first vector in the second vector. PS. Of course, I would much prefer a dataframe to a matrix... > * Sam Steingold <f...@tah.bet> [2012-02-08 15:56:12 -0500]: > > To be clear, I can do that with nested for loops: > > v <- c("A1B2","A3C4","B5","C6A7B8") > l <- strsplit(gsub("(.{2})","\\1,",v),",") > d <- data.frame(A=vector(length=4,mode="integer"), > B=vector(length=4,mode="integer"), > C=vector(length=4,mode="integer")) > > for (i in 1:length(l)) { > l1 <- l[[i]] > for (j in 1:length(l1)) { > d[[substring(l1[j],1,1)]][i] <- as.numeric(substring(l1[j],2,2)) > } > } > > > but I am afraid that handling 1,000,000 (=length(unlist(l))) strings in > a loop will kill me. > > >> * Sam Steingold <f...@tah.bet> [2012-02-08 15:34:38 -0500]: >> >> Suppose I have a vector of strings: >> c("A1B2","A3C4","B5","C6A7B8") >> [1] "A1B2" "A3C4" "B5" "C6A7B8" >> where each string is a sequence of <column><value> pairs >> (fixed width, in this example both value and name are 1 character, in >> reality the column name is 6 chars and value is 2 digits). >> I need to convert it to a data frame: >> data.frame(A=c(1,3,0,7),B=c(2,0,5,8),C=c(0,4,0,6)) >> A B C >> 1 1 2 0 >> 2 3 0 4 >> 3 0 5 0 >> 4 7 8 6 >> >> how do I do that? >> thanks. -- Sam Steingold (http://sds.podval.org/) on Ubuntu 11.10 (oneiric) X 11.0.11004000 http://honestreporting.com http://truepeace.org http://openvotingconsortium.org http://iris.org.il http://jihadwatch.org http://camera.org Failure is not an option. It comes bundled with your Microsoft product. ______________________________________________ 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.