[R] using "table" in R

[Prof Brian Ripley]

On Sun, 17 Sep 2006, jim holtman wrote:

> You can use 'names'
>
>> d = as.data.frame(matrix(c(1, 2, 3, 3), 2,2))
>>
>> x <- table(unlist(d))
>> x
>
> 1 2 3
> 1 1 2
>> names(x)
> [1] "1" "2" "3"

You can, but Søren was equally correct: names() on a 1D array actually 
looks up the dimnames.  OTOH, we do really want to encourage people to use 
the accessor functions, so

> dimnames(x)[[1]]
[1] "1" "2" "3"

is better supported.


> On 9/17/06, Søren Merser <merser at image.dk> wrote:
>> hi, here's a way:
>>> attr(table(unlist(d)),'dimnames')[[1]]
>> [1] "1" "2" "3"
>>> as.numeric(table(unlist(d)))
>> [1] 1 1 2

You don't need as.numeric here: as.vector will remove the attributes if 
that is the intention.


>> soren
>>
>> ----- Original Message -----
>> From: "Bingshan Li" <bingshanli at yahoo.com>
>> To: "jim holtman" <jholtman at gmail.com>
>> Cc: <r-help at stat.math.ethz.ch>
>> Sent: Sunday, September 17, 2006 6:14 AM
>> Subject: Re: [R] using "table" in R
>>
>>
>>> Hi Jim,
>>>
>>> This is the way to get the frequencies. But what I
>>> want is to store the elements in one vector and their
>>> frequencies in another vector. My problem is that when
>>> I call "table" to return the frequency table, I do not
>>> know how to extract these two vectors. I tried
>>> table(...)$dinnames and it did not work. It returned
>>> NULL.
>>>
>>> Thanks!
>>>
>>>
>>> --- jim holtman <jholtman at gmail.com> wrote:
>>>
>>>> Here is one way; you create a vector of the data in
>>>> the dataframe with
>>>> 'unlist' and then use table:
>>>>
>>>>> d = as.data.frame(matrix(c(1, 2, 3, 3), 2,2))
>>>>> d
>>>>   V1 V2
>>>> 1  1  3
>>>> 2  2  3
>>>>> table(unlist(d))
>>>>
>>>> 1 2 3
>>>> 1 1 2
>>>>>
>>>>
>>>>
>>>> On 9/16/06, Bingshan Li <bingshanli at yahoo.com>
>>>> wrote:
>>>>> Hi there,
>>>>>
>>>>> I have a dataframe whose elements are numbers or
>>>>> characters. I want to extract the frequencies of
>>>> each
>>>>> elements in the dataframe. For example,
>>>>>
>>>>> d = as.data.frame(matrix(c(1, 2, 3, 3), 2,2))
>>>>>
>>>>> What I want is first what are the elements in the
>>>> data
>>>>> (1,2,3 here) and second what are their frequencies
>>>>> (1,1,2 respectively). How to use "table" to
>>>> extract
>>>>> these two pieces of information? I played with
>>>> "table"
>>>>> but couldn't extract the information. Please
>>>> assume
>>>>> that we do not know how many elements in the
>>>> dataframe
>>>>> a priori.
>>>>>
>>>>> Thanks a lot!
>>>>>
>>>>> ______________________________________________
>>>>> R-help at stat.math.ethz.ch 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.
>>>>>
>>>>
>>>>
>>>> --
>>>> Jim Holtman
>>>> Cincinnati, OH
>>>> +1 513 646 9390
>>>>
>>>> What is the problem you are trying to solve?
>>>>
>>>
>>> ______________________________________________
>>> R-help at stat.math.ethz.ch 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.
>>
>> ______________________________________________
>> R-help at stat.math.ethz.ch 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.
>>
>
>
>

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595