R help - Jun 2009 - how to checking whether elements of a vector changed or not.

Hello,

I have a vector:
x <- c("A", "A", "A", "B",
"A", "A", "C")

I'd like to compare each of elements of vector x from its previous element
(except for the 1st element which does not have previous element). So I'd
like to get a vector y (of same length) that looks something like
(0, 0, 0, 1, 1, 0, 1) or
(F, F, F, T, T, F, T)

Is there a command that do this? 

I was thinking to construct another variable x1 from x as follows:
x1 <- vector(length=length(x))
x1[1] <- x[1]
x1[2:length(x)] <- x[1:(length(x)-1)]
x1

Now, x1 is ("A" "A" "B" "B"
"B" "A"). However, I don't know how to compare 2
vectors (of same length) elements by elements and a vector that indicates
change or no change.

Or there is a easier way to do this? 

Thank you very much
Julia



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Try this:

c(FALSE, !!diff(c(factor(x))))


On Mon, Jun 1, 2009 at 11:57 AM, liujb <liujulia7 at yahoo.com>
wrote:
>
> Hello,
>
> I have a vector:
> x <- c("A", "A", "A", "B",
"A", "A", "C")
>
> I'd like to compare each of elements of vector x from its previous
element
> (except for the 1st element which does not have previous element). So
I'd
> like to get a vector y (of same length) that looks something like
> (0, 0, 0, 1, 1, 0, 1) or
> (F, F, F, T, T, F, T)
>
> Is there a command that do this?
>
> I was thinking to construct another variable x1 from x as follows:
> x1 <- vector(length=length(x))
> x1[1] <- x[1]
> x1[2:length(x)] <- x[1:(length(x)-1)]
> x1
>
> Now, x1 is ("A" "A" "B" "B"
"B" "A"). However, I don't know how to compare 2
> vectors (of same length) elements by elements and a vector that indicates
> change or no change.
>
> Or there is a easier way to do this?
>
> Thank you very much
> Julia
>
>
>
> --
> View this message in context:
http://www.nabble.com/how-to-checking-whether-elements-of-a-vector-changed-or-not.-tp23817310p23817310.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at 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.
>

> c(x[1], x[-length(x)]) != x
[1] FALSE FALSE FALSE  TRUE  TRUE FALSE  TRUE

On Mon, Jun 1, 2009 at 11:57 PM, liujb <liujulia7 at yahoo.com>
wrote:
>
> Hello,
>
> I have a vector:
> x <- c("A", "A", "A", "B",
"A", "A", "C")
>
> I'd like to compare each of elements of vector x from its previous
element
> (except for the 1st element which does not have previous element). So
I'd
> like to get a vector y (of same length) that looks something like
> (0, 0, 0, 1, 1, 0, 1) or
> (F, F, F, T, T, F, T)
>
> Is there a command that do this?
>
> I was thinking to construct another variable x1 from x as follows:
> x1 <- vector(length=length(x))
> x1[1] <- x[1]
> x1[2:length(x)] <- x[1:(length(x)-1)]
> x1
>
> Now, x1 is ("A" "A" "B" "B"
"B" "A"). However, I don't know how to compare 2
> vectors (of same length) elements by elements and a vector that indicates
> change or no change.
>
> Or there is a easier way to do this?
>
> Thank you very much
> Julia
>
>
>
> --
> View this message in context:
http://www.nabble.com/how-to-checking-whether-elements-of-a-vector-changed-or-not.-tp23817310p23817310.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at 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.
>