R help - Feb 2003 - position of an element in a vector

Hello.  Sorry for the elementary post.  I've looked through the 
documentation, but can't seem to find a function which allows one to 
extract the position of an element within a list...for example the position 
of the element 4 in the vector c(1,2,4,3,6) is 3.  Thanks much for any help.

   Jason

How about:

 > x <- c(1, 2, 4, 3, 6)
 > (1:length(x))[x==4]
[1] 3

Spencer Graves

Jason Bond wrote:
> Hello.  Sorry for the elementary post.  I've looked through the 
> documentation, but can't seem to find a function which allows one to 
> extract the position of an element within a list...for example the 
> position of the element 4 in the vector c(1,2,4,3,6) is 3.  Thanks much 
> for any help.
> 
>   Jason
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> http://www.stat.math.ethz.ch/mailman/listinfo/r-help

For extracting list elements, you can use the [[ operator, as in

a <- list(6, 5, 4, 3)
a[[1]] ## get '6'

For vectors, you can use [, as in

a <- c(1,2,4,3,6)
a[3]

-roger
_______________________________
UCLA Department of Statistics
rpeng at stat.ucla.edu
http://www.stat.ucla.edu/~rpeng

On Thu, 13 Feb 2003, Jason Bond wrote:
> Hello.  Sorry for the elementary post.  I've looked through the 
> documentation, but can't seem to find a function which allows one to 
> extract the position of an element within a list...for example the position
> of the element 4 in the vector c(1,2,4,3,6) is 3.  Thanks much for any
help.
> 
>    Jason
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> http://www.stat.math.ethz.ch/mailman/listinfo/r-help
>

>-----Original Message-----
>From: r-help-admin at stat.math.ethz.ch 
>[mailto:r-help-admin at stat.math.ethz.ch] On Behalf Of Jason Bond
>Sent: Thursday, February 13, 2003 3:41 PM
>To: R-help at stat.math.ethz.ch
>Subject: [R] position of an element in a vector
>
>
>Hello.  Sorry for the elementary post.  I've looked through the 
>documentation, but can't seem to find a function which allows one to 
>extract the position of an element within a list...for example 
>the position 
>of the element 4 in the vector c(1,2,4,3,6) is 3.  Thanks much 
>for any help.
>
>   Jason
Take a look at ?which.

For example:
> which(c(1,2,4,3,6) == 4)
[1] 3


Regards,

Marc

?which

On Thursday 13 February 2003 03:40 pm, Jason Bond wrote:
> Hello.  Sorry for the elementary post.  I've looked through the
> documentation, but can't seem to find a function which allows one to
> extract the position of an element within a list...for example the position
> of the element 4 in the vector c(1,2,4,3,6) is 3.  Thanks much for any
> help.
>
>    Jason
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> http://www.stat.math.ethz.ch/mailman/listinfo/r-help

Hello,

   I'm a recovering xlispstat user, and am trying to become a good R 
user.  I've looked around on the CRAN doc website and have found quite a 
few sets of documentation with various level of data manipulation function 
descriptions (of what I've seen, most relatively low levels), and many with 
examples of Rs use in statistical analyses.  Although I don't expect to get 
my wish, ideally, it would be nice to have some sort of data manipulation 
function guide for programmers.  I guess I'm somewhat of a different case, 
as I know which functions that I want to use...I just don't know their 
names...for example, all those great xlispstat functions like:

remove-duplicates
sort-data
combine
remove
reverse
butlast
first
case
which
mapcar
map-elements
all the string functions
and many many more,

descriptions of a few of which are spread out in various documents.  Part 
of my problem is clinging to that which I know.  Anyway, any general advice 
would be greatly appreciated.

   Jason

At 03:57 PM 2/13/03 -0600, you wrote:
>?which
>
>On Thursday 13 February 2003 03:40 pm, Jason Bond wrote:
> > Hello.  Sorry for the elementary post.  I've looked through the
> > documentation, but can't seem to find a function which allows one
to
> > extract the position of an element within a list...for example the
position
> > of the element 4 in the vector c(1,2,4,3,6) is 3.  Thanks much for any
> > help.
> >
> >    Jason
> >
> > ______________________________________________
> > R-help at stat.math.ethz.ch mailing list
> > http://www.stat.math.ethz.ch/mailman/listinfo/r-help