R help - Jul 2011 - How to count numbers of a vector and use them as index values?

Dear R folks,


I am sorry to ask this simple question, but my search for the right
way/command was unsuccessful.

I have a vector
> x <- c(2, 2, 3, 3, 4, 6)
Now the values of x should be considered the index of another vector
with possible greater length, say 8, and the value should be how often
the indexes appeared in the original vector x.
> length(result)
 [1] 8
> result
 [1] 0 2 2 1 0 1 0 0


Thank you in advance,

Paul
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 198 bytes
Desc: This is a digitally signed message part
URL:
<https://stat.ethz.ch/pipermail/r-help/attachments/20110731/347cca14/attachment.bin>

Hi Paul,

I would use something like this:
> x <- c(2,2,3,3,4,6)
> table(x)
x
2 3 4 6
2 2 1 1
> x <- factor(x, levels=1:8)
> table(x)
x
1 2 3 4 5 6 7 8
0 2 2 1 0 1 0 0

Sarah

On Sun, Jul 31, 2011 at 5:41 PM, Paul Menzel
<paulepanter at users.sourceforge.net> wrote:
> Dear R folks,
>
>
> I am sorry to ask this simple question, but my search for the right
> way/command was unsuccessful.
>
> I have a vector
>
>> x <- c(2, 2, 3, 3, 4, 6)
>
> Now the values of x should be considered the index of another vector
> with possible greater length, say 8, and the value should be how often
> the indexes appeared in the original vector x.
>
>> length(result)
> ?[1] 8
>> result
> ?[1] 0 2 2 1 0 1 0 0
>
>
> Thank you in advance,
>
> Paul
>


-- 
Sarah Goslee
http://www.functionaldiversity.org

Here's an attempt using sapply:
> x <- c(2, 2, 3, 3, 4, 6)
> ys <- 1:8
> sapply(ys, function(y) { length(which(x==y)) } )
[1] 0 2 2 1 0 1 0 0

Jeff

On Sun, Jul 31, 2011 at 2:41 PM, Paul Menzel
<paulepanter at users.sourceforge.net> wrote:
> Dear R folks,
>
>
> I am sorry to ask this simple question, but my search for the right
> way/command was unsuccessful.
>
> I have a vector
>
>> x <- c(2, 2, 3, 3, 4, 6)
>
> Now the values of x should be considered the index of another vector
> with possible greater length, say 8, and the value should be how often
> the indexes appeared in the original vector x.
>
>> length(result)
> ?[1] 8
>> result
> ?[1] 0 2 2 1 0 1 0 0
>
>
> Thank you in advance,
>
> Paul
>
> ______________________________________________
> 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.
>
>

See also ?tabulate.

tabulate(x,8)


> Hi Paul,
>
> I would use something like this:
>
>> x <- c(2,2,3,3,4,6)
>> table(x)
> x
> 2 3 4 6
> 2 2 1 1
>> x <- factor(x, levels=1:8)
>> table(x)
> x
> 1 2 3 4 5 6 7 8
> 0 2 2 1 0 1 0 0
>
> Sarah
>
> On Sun, Jul 31, 2011 at 5:41 PM, Paul Menzel
> <paulepanter at users.sourceforge.net> wrote:
>> Dear R folks,
>>
>>
>> I am sorry to ask this simple question, but my search for the right
>> way/command was unsuccessful.
>>
>> I have a vector
>>
>>> x <- c(2, 2, 3, 3, 4, 6)
>>
>> Now the values of x should be considered the index of another vector
>> with possible greater length, say 8, and the value should be how often
>> the indexes appeared in the original vector x.
>>
>>> length(result)
>> ?[1] 8
>>> result
>> ?[1] 0 2 2 1 0 1 0 0
>>
>>
>> Thank you in advance,
>>
>> Paul
>>
>
>
>
> --
> Sarah Goslee
> http://www.functionaldiversity.org
>
> ______________________________________________
> 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.
>

Dear Sarah,


Am Sonntag, den 31.07.2011, 18:10 -0400 schrieb Sarah Goslee:
> I would use something like this:
> 
> > x <- c(2,2,3,3,4,6)
> > table(x)
> x
> 2 3 4 6
> 2 2 1 1
> > x <- factor(x, levels=1:8)
> > table(x)
> x
> 1 2 3 4 5 6 7 8
> 0 2 2 1 0 1 0 0
awesome. Thank you.

Looking further I found the article ?Thinking in R: vectors? on
R-bloggers [1]. The given example there returned a list though by using
`lapply()` and the author is asking at the end: ?Any R experts out there
with suggestions for a non-lapply solution??. So Derek-Jones, Sarah just
gave you the answer.

A further note regarding the example in [1], instead of

	length(X[X == n])

to count the number of occurrences you can also use `sum(X == n)`
relying on the fact that `TRUE` and `FALSE` are converted to the
integers `1` and `0`.


Thanks,

Paul


[1] http://www.r-bloggers.com/thinking-in-r-vectors/
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 198 bytes
Desc: This is a digitally signed message part
URL:
<https://stat.ethz.ch/pipermail/r-help/attachments/20110801/05d1aa33/attachment.bin>