OK, I'm pre-coffee, but what's wrong with using upper.tri to create a new matrix and then multiplying that matrix by the original "dat" matrix (direct multiplication, not matrix multiply) to get the desired answer?
Bert Gunter wrote > I believe matrix indexing makes Arun's complex code wholly unnececessary: > > Starting with dat1 as above: > > m <- matrix(0,4,4) > m[as.matrix(dat1[,1:2])] <- dat1[,3] > > ## yielding: > m > > [,1] [,2] [,3] [,4] > [1,] 0 2 1 1 > [2,] 0 1 2 1 > [3,] 0 0 0 2 > [4,] 0 0 0 0 > > If you want to get rid of any nonzero diagonal entries: > > diag(m) <- 0 ## does it. > > Cheers, > Bert > > > > > > On Sun, Nov 17, 2013 at 10:27 AM, arun < > smartpink111@ > > wrote: >> Hi, >> May be this helps: >> >> dat1 <- read.table(text=" >> data data freq >> 1 2 2 >> 1 3 1 >> 1 4 1 >> 2 3 2 >> 2 4 1 >> 2 2 1 >> 3 4 2",sep="",header=TRUE) >> val<- unique(c(dat1[,1],dat1[,2])) >> dat2 <-expand.grid(data=val,data.1=val) >> library(plyr) >> library(reshape2) >> res <- dcast(join(dat2,dat1),data~data.1,value.var="freq",fill=0) >> row.names(res) <- res[,1] >> res1 <- as.matrix(res[,-1]) >> diag(res1) <-0 >> >> #or >> m1 <- matrix(0,length(val),length(val),dimnames=list(val,val)) >> >> indx1 <- outer(colnames(m1),rownames(m1),paste,sep="") >> indx2 <- paste0(dat1[,1],dat1[,2]) >> m1[match(indx2,indx1)] <- dat1[,3] >> diag(m1) <- 0 >> m1 >> # 1 2 3 4 >> #1 0 2 1 1 >> #2 0 0 2 1 >> #3 0 0 0 2 >> #4 0 0 0 0 >> >> A.K. >> >> >> Hello , >> I am working on a project , >> i need to create an upper triangular matrix from the data in this form; >> data data freq >> 1 2 2 >> 1 3 1 >> 1 4 1 >> 2 3 2 >> 2 4 1 >> 2 2 1 >> 3 4 2 >> >> to a triangular matrix in the following form : >> 1 2 3 4 >> 1 0 2 1 1 >> 2 0 0 2 1 >> 3 0 0 0 2 >> 4 0 0 0 0 >> >> i am new to R please help >> >> >> ______________________________________________ >> > R-help@ > 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. > > > > -- > > Bert Gunter > Genentech Nonclinical Biostatistics > > (650) 467-7374 > > ______________________________________________ > R-help@ > 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. -- View this message in context: http://r.789695.n4.nabble.com/creating-upper-triangular-matrix-tp4680632p4680674.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ 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.
