Let's say i have a = c(1, 4, 5) b = c(2, 6, 7) and i have matrix m, what's an efficient way of access m[1, 2], m[4, 6], m[5, 7] like of course m[a, b] = is not going to do, but what's an expression that will allow me to have that list? Thanks! -- View this message in context: http://www.nabble.com/Simplest-question-ever...-tf3329894.html#a9258932 Sent from the R help mailing list archive at Nabble.com.
I'm not sure this is the most efficient, but how about: diag(m[a,b]) ? On 3/1/07, yoooooo <magno_yu at ml.com> wrote:> > Let's say i have > > a = c(1, 4, 5) > b = c(2, 6, 7) > > and i have matrix m, what's an efficient way of access > m[1, 2], m[4, 6], m[5, 7] > like of course m[a, b] = is not going to do, but what's an expression that > will allow me to have that list? > > Thanks! > -- > View this message in context: http://www.nabble.com/Simplest-question-ever...-tf3329894.html#a9258932 > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help at stat.math.ethz.ch 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. >
try:> a = c(1, 4, 5) > b = c(2, 6, 7) > > m <- matrix(1:49,7,7) > m[cbind(a,b)] # 'array' indexing[1] 8 39 47> m[,1] [,2] [,3] [,4] [,5] [,6] [,7] [1,] 1 8 15 22 29 36 43 [2,] 2 9 16 23 30 37 44 [3,] 3 10 17 24 31 38 45 [4,] 4 11 18 25 32 39 46 [5,] 5 12 19 26 33 40 47 [6,] 6 13 20 27 34 41 48 [7,] 7 14 21 28 35 42 49>Jim Holtman "What is the problem you are trying to solve?" ----- Original Message ---- From: yoooooo <magno_yu@ml.com> To: r-help@stat.math.ethz.ch Sent: Thursday, March 1, 2007 4:28:02 PM Subject: [R] Simplest question ever... Let's say i have a = c(1, 4, 5) b = c(2, 6, 7) and i have matrix m, what's an efficient way of access m[1, 2], m[4, 6], m[5, 7] like of course m[a, b] = is not going to do, but what's an expression that will allow me to have that list? Thanks! -- View this message in context: http://www.nabble.com/Simplest-question-ever...-tf3329894.html#a9258932 Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help@stat.math.ethz.ch 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. ____________________________________________________________________________________ Access over 1 million songs. [[alternative HTML version deleted]]
If I understand it correctly, you mean to say>a = c(1, 4, 5) >b = c(2, 6, 7)and m<- rbind(a,b) if you want to see a particular column you can try m[,1] hope it helps, -GS On 3/2/07, yoooooo <magno_yu@ml.com> wrote:> > > Let's say i have > > a = c(1, 4, 5) > b = c(2, 6, 7) > > and i have matrix m, what's an efficient way of access > m[1, 2], m[4, 6], m[5, 7] > like of course m[a, b] = is not going to do, but what's an expression that > will allow me to have that list? > > Thanks! > -- > View this message in context: > http://www.nabble.com/Simplest-question-ever...-tf3329894.html#a9258932 > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help@stat.math.ethz.ch 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. >[[alternative HTML version deleted]]