[R] array manipulation simple questions
Hi there, I am pretty new to R. Actually I started using it yesterday. I have two questions: 1. Suppose I have a<-c(1:10) (or a<-array(c(1:10),dim=c(1,10))) and I want to end up with vector b=[0 0 0 0 0 1 1 1 1 1]. i.e. I want to substitute alla elements that are <5 with 0 and >5 with 1. I did this by using a for loop. Is there another function to use so as to avoid the "for"? 2. Suppose I have a<-c(1,1,2,2,3,3) (or array again) And I want to place a "4,5" before every "2" and end up with a new "bigger" vector "b": b=[1 1 4 5 2 4 5 2 3 3] Also I want to find where the 2's in array "a" (if it was an array) are located i.e. positions 3,4. Thanx very much in advance!! P.S: Will you inform me via mail or should I visit any blog and post there my questions? ___ ×ñçóéìïðïéåßôå Yahoo!; ÂáñåèÞêáôå ôá åíï÷ëçôéêÜ ìçíýìáôá (spam); Ôï Yahoo! Mail äéáèÝôåé ôçí êáëýôåñç äõíáôÞ ðñïóôáóßá êáôÜ ôùí åíï÷ëçôéêþí ìçíõìÜôùí http://login.yahoo.com/config/mail?.intl=gr [[alternative HTML version deleted]] __ 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.
Re: [R] array manipulation simple questions
Λεωνίδας Μπαντής wrote: > > 1. Suppose I have a<-c(1:10) (or a<-array(c(1:10),dim=c(1,10))) > > and I want to end up with vector b=[0 0 0 0 0 1 1 1 1 1]. i.e. I want to > substitute alla elements that are <5 with 0 and >5 with 1. > I think you mean >=5, not > 5. In that case, try this: b <- ifelse( a < 5, 0, 1) Λεωνίδας Μπαντής wrote: > > 2. Suppose I have a<-c(1,1,2,2,3,3) (or array again) > > And I want to place a "4,5" before every "2" and end up with a new > "bigger" vector "b": > > b=[1 1 4 5 2 4 5 2 3 3] > > Also I want to find where the 2's in array "a" (if it was an array) are > located i.e. positions 3,4. > Not sure how to insert the 4,5, but this will find the where the 2's are: which(a == 2) -- View this message in context: http://www.nabble.com/array-manipulation-simple-questions-tp22173710p22175864.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.
Re: [R] array manipulation simple questions
2009/2/23 Λεωνίδας Μπαντής : > > Hi there, > > I am pretty new to R. Actually I started using it yesterday. I have two > questions: > > 1. Suppose I have a<-c(1:10) (or a<-array(c(1:10),dim=c(1,10))) > > and I want to end up with vector b=[0 0 0 0 0 1 1 1 1 1]. i.e. I want to > substitute alla elements that are <5 with 0 and >5 with 1. > > I did this by using a for loop. Is there another function to use so as to > avoid the "for"? (a>5)+0 # or out <- as.numeric(a > 5) if (is.matrix(a)) out <- matrix(a, 1) out > > > 2. Suppose I have a<-c(1,1,2,2,3,3) (or array again) > > And I want to place a "4,5" before every "2" and end up with a new "bigger" > vector "b": > > b=[1 1 4 5 2 4 5 2 3 3] # return c(4, 5, 2) or x f <- function(x) if (x==2) c(4:5, x) else x # apply f to each element and # if a is a matrix make output a matrix too out <- unlist(sapply(a, f)) if (is.matrix(a)) out <- matrix(out, nrow(a)) out > > Also I want to find where the 2's in array "a" (if it was an array) are > located i.e. positions 3,4. which(a == 2) __ 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.
Re: [R] array manipulation simple questions
On Feb 24, 3:57 pm, jdeisenberg wrote: > Λεωνίδας Μπαντής wrote: > > > 1. Suppose I have a<-c(1:10) (or a<-array(c(1:10),dim=c(1,10))) > > > and I want to end up with vector b=[0 0 0 0 0 1 1 1 1 1]. i.e. I want to > > substitute alla elements that are <5 with 0 and >5 with 1. > > I think you mean >=5, not > 5. In that case, try this: > > b <- ifelse( a < 5, 0, 1) you could also use b <- 1*(x >= 5) #the logical elements get converted to numeric > > Λεωνίδας Μπαντής wrote: > > > 2. Suppose I have a<-c(1,1,2,2,3,3) (or array again) > > > And I want to place a "4,5" before every "2" and end up with a new > > "bigger" vector "b": > > > b=[1 1 4 5 2 4 5 2 3 3] > > > Also I want to find where the 2's in array "a" (if it was an array) are > > located i.e. positions 3,4. > > Not sure how to insert the 4,5, but this will find the where the 2's are: > which(a == 2) > you could use b <- rep(a,times = 2*(a==2) + 1) replace(b, which(b==2), c(4,5,2)) > -- > View this message in > context:http://www.nabble.com/array-manipulation-simple-questions-tp22173710p... > Sent from the R help mailing list archive at Nabble.com. > > __ > r-h...@r-project.org mailing listhttps://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guidehttp://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.
