R help - Apr 2010 - table command

Hi,

 

Let s be a dataframe. 

 
> s
   A B C

   0 0 1

   1 0 1

   1 0 1

   0 0 1

   1 0 1

   0 1 1

   0 1 1

   0 1 1

   0 0 1

 
> tab1=table(s[,c(1,2)])
> tab1
   B

A   0 1

  0 3 3

  1 3 0

 
> tab2=table(s[,c(1,3)])
> tab2
   C

A   1

  0 6

  1 3

 

 

The problem is I need to access frequency corresponding to (0,0).
tab1[1] will give me the correct value while tab2[1] will not give the
frequency which I expected. So, is there a possibility in the table
command to have the order of tab1 and tab2 being equal? (here 2*2). May
be by filling in the appropriate value as 0 or NA?

 

Thanks,

Shubha

 

This e-mail may contain confidential and/or privileged i...{{dropped:13}}

On Apr 24, 2010, at 8:59 AM, Shubha Vishwanath Karanth wrote:
> Hi,
> 
> 
> 
> Let s be a dataframe. 
> 
> 
> 
>> s
> 
>   A B C
> 
>   0 0 1
> 
>   1 0 1
> 
>   1 0 1
> 
>   0 0 1
> 
>   1 0 1
> 
>   0 1 1
> 
>   0 1 1
> 
>   0 1 1
> 
>   0 0 1
> 
> 
> 
>> tab1=table(s[,c(1,2)])
> 
>> tab1
> 
>   B
> 
> A   0 1
> 
>  0 3 3
> 
>  1 3 0
> 
> 
> 
>> tab2=table(s[,c(1,3)])
> 
>> tab2
> 
>   C
> 
> A   1
> 
>  0 6
> 
>  1 3
> 
> 
> 
> 
> 
> The problem is I need to access frequency corresponding to (0,0).
> tab1[1] will give me the correct value while tab2[1] will not give the
> frequency which I expected. So, is there a possibility in the table
> command to have the order of tab1 and tab2 being equal? (here 2*2). May
> be by filling in the appropriate value as 0 or NA?
> 
> 
> 
> Thanks,
> 
> Shubha

In this case, 'C' has no 0's, so that value is not considered in the
tabulation in the second table.

If you coerce each column to a factor with common levels, then you can obtain
consistent formats for the output of table. Even though there are no 0's in
'C', that 'C' as a factor now has levels of 0 and 1, they will
both be included in the table() output.


s.new <- data.frame(lapply(s, factor, levels = 0:1))
> str(s.new)
'data.frame':	9 obs. of  3 variables:
 $ A: Factor w/ 2 levels "0","1": 1 2 2 1 2 1 1 1 1
 $ B: Factor w/ 2 levels "0","1": 1 1 1 1 1 2 2 2 1
 $ C: Factor w/ 2 levels "0","1": 2 2 2 2 2 2 2 2 2
> s.new
  A B C
1 0 0 1
2 1 0 1
3 1 0 1
4 0 0 1
5 1 0 1
6 0 1 1
7 0 1 1
8 0 1 1
9 0 0 1

> table(s.new[, c(1, 2)])
   B
A   0 1
  0 3 3
  1 3 0
> table(s.new[, c(1, 3)])
   C
A   0 1
  0 0 6
  1 0 3


See ?factor, ?lapply and ?data.frame

HTH,

Marc Schwartz

Is the fact that 0 is a possible and interesting value (even in being absent) a
property of the table? Or a property of the variable?

I would argue that it is probably a property of the variable, and this is the
better way to work with it in R (some older programs forced us to specify this
at the analysis stage and it can take a bit of an effort to break that habit and
do the more sensible approach).

I would convert your data to factors (or ordered factors) and specify the
levels, then table just works on its own:

# untested code
> s2 <- as.data.frame( lapply(s, function(x) factor(x, levels=0:1) ) )
> table( s2[,c(1,3)] )
Hope this helps,

-- 
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org
801.408.8111

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Shubha Vishwanath Karanth
> Sent: Saturday, April 24, 2010 7:59 AM
> To: r-help at r-project.org; r-help at stat.math.ethz.ch
> Subject: [R] table command
> 
> Hi,
> 
> 
> 
> Let s be a dataframe.
> 
> 
> 
> > s
> 
>    A B C
> 
>    0 0 1
> 
>    1 0 1
> 
>    1 0 1
> 
>    0 0 1
> 
>    1 0 1
> 
>    0 1 1
> 
>    0 1 1
> 
>    0 1 1
> 
>    0 0 1
> 
> 
> 
> > tab1=table(s[,c(1,2)])
> 
> > tab1
> 
>    B
> 
> A   0 1
> 
>   0 3 3
> 
>   1 3 0
> 
> 
> 
> > tab2=table(s[,c(1,3)])
> 
> > tab2
> 
>    C
> 
> A   1
> 
>   0 6
> 
>   1 3
> 
> 
> 
> 
> 
> The problem is I need to access frequency corresponding to (0,0).
> tab1[1] will give me the correct value while tab2[1] will not give the
> frequency which I expected. So, is there a possibility in the table
> command to have the order of tab1 and tab2 being equal? (here 2*2). May
> be by filling in the appropriate value as 0 or NA?
> 
> 
> 
> Thanks,
> 
> Shubha
> 
> 
> 
> This e-mail may contain confidential and/or privileged
> i...{{dropped:13}}
> 
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