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?
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???????? ??????? 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) ???????? ??????? 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.
2009/2/23 ???????? ??????? <bleonidas25 at yahoo.gr>:> > 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)