R help - Jan 2011 - creating categorical frequency tables from continuous data

Hello,

I am working with a dataset which essentially has only one column - a 
list of distances in metres, accurate to several decimal places. eg

distance
1000
6403.124
1000
1414.214
1414.214
1000

I want to organise this into a frequency table, grouping into categories 
of 0 - 999,  1000 - 1999, 2000-2999 etc. I'd also like the rows where 
there are no data points in that category to contain 0, in order to be 
able to plot a histrogram with a linear x axis, and to statistically 
analyse differences between datasets.

I have tried table()  which doesn't group the data the way I'd like it, 
I've also tried cut() but couldn't make it work. Ideally I'd like
the
output to look something like this...

distance        frequency
0-999            0
1000-1999   3
2000-2999   0
...

Any suggestions that are an improvement on doing it manually please?

Thanks in advance!

Louise

On 11-01-27 14:58, Louise Mair wrote:
> Hello,
>
> I am working with a dataset which essentially has only one column - a list
of
> distances in metres, accurate to several decimal places. eg
>
> distance
> 1000
> 6403.124
> 1000
> 1414.214
> 1414.214
> 1000
>
> I want to organise this into a frequency table, grouping into categories of
0
> - 999,  1000 - 1999, 2000-2999 etc. I'd also like the rows where there
are no
> data points in that category to contain 0, in order to be able to plot a 
> histrogram with a linear x axis, and to statistically analyse differences 
> between datasets.
>
> I have tried table()  which doesn't group the data the way I'd like
it, I've
> also tried cut() but couldn't make it work. Ideally I'd like the
output to
> look something like this...
>
> distance        frequency
> 0-999            0
> 1000-1999   3
> 2000-2999   0
> ...
Could be a starting point for testing:

x <- abs(rnorm(500, 5000, 3000)
br <- seq(0, 20000, 1000)
summary(cut(x, br, labels=br[-1], include.lowest=T, 
ordered_result=T))

Look at ?cut to find out more. Good luck, *S*
>
> Any suggestions that are an improvement on doing it manually please?
>
> Thanks in advance!
>
> Louise
>
> ______________________________________________
> 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.
>
>
-- 
Sascha Vieweg, saschaview at gmail.com

Hi:

Using your data below as the template,

u <- cut(x, breaks = c(0, seq(1000, 7000, by = 1000)), dig.lab = 4, right
FALSE)
as.data.frame(table(u))
            u Freq
1    [0,1000)    0
2 [1000,2000)    5
3 [2000,3000)    0
4 [3000,4000)    0
5 [4000,5000)    0
6 [5000,6000)    0
7 [6000,7000)    1

It makes no sense to use labels like 0 - 999, 1000 - 1999, etc. when your
values are continuous. If you round or truncate them, you can define cut()
the same way as above and use the labels argument to format the labels as
you wish, something like

labs <- c('0-999', '1000-1999', '2000-2999',
'3000-3999', '4000-4999',
'5000-5999', '6000-6999')
v <- cut(x, breaks = c(0, seq(1000, 7000, by = 1000)), labels = labs, right
= FALSE)
as.data.frame(table(v))

HTH,
Dennis

On Thu, Jan 27, 2011 at 6:58 AM, Louise Mair <lm609@york.ac.uk> wrote:
> Hello,
>
> I am working with a dataset which essentially has only one column - a list
> of distances in metres, accurate to several decimal places. eg
>
> distance
> 1000
> 6403.124
> 1000
> 1414.214
> 1414.214
> 1000
>
> I want to organise this into a frequency table, grouping into categories of
> 0 - 999,  1000 - 1999, 2000-2999 etc. I'd also like the rows where
there are
> no data points in that category to contain 0, in order to be able to plot a
> histrogram with a linear x axis, and to statistically analyse differences
> between datasets.
>
> I have tried table()  which doesn't group the data the way I'd like
it,
> I've also tried cut() but couldn't make it work. Ideally I'd
like the output
> to look something like this...
>
> distance        frequency
> 0-999            0
> 1000-1999   3
> 2000-2999   0
> ...
>
> Any suggestions that are an improvement on doing it manually please?
>
> Thanks in advance!
>
> Louise
>
> ______________________________________________
> R-help@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.
>
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